Polynomial fit returns infinity and NaN as parameters

[StevanOgnjanovic]

As already posted on stackoverflow (https://stackoverflow.com/q/77803357/19921514) I'm having issues with 6th order polynomial fit of 100 datapoints.

I'm using Svd decomposition to get the most acurate results, but on some datasets, this results in the polynomial parameters being infinity and NaN. On other datasets the fit works as expected.

Here's the code:
double[] PolFitCoeff = Fit.Polynomial(XValues, YValues, 6, MathNet.Numerics.LinearRegression.DirectRegressionMethod.Svd);

and a few datasets:

double[] XWorking1 = new double[] {370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470};
double[] YWorking1 = new double[] {-0.00227, 0, 0, 0.004547, 0, 0.010239, 0.007965, 0.002276, 0.007967, 0.002276, 0.002277, 0.001139, 0.00114, 0.025087, 0.01027, 0.044447, 0.157399, 0.143755, 0.142648, 0.138106, 0.135882, 0.132488, 0.133655, 0.131388, 0.133708, 0.144043, 0.166937, 0.221899, 0.334092, 0.549274, 0.926127, 1.543659, 2.490492, 3.847829, 5.696928, 8.066181, 10.973218, 14.358651, 18.197052, 22.374146, 26.828288, 31.416559, 36.102365, 40.708982, 45.16626, 49.463491, 53.530264, 57.321396, 60.836134, 64.075579, 67.014809, 69.689847, 72.089191, 74.240713, 76.18411, 77.900317, 79.423356, 80.750665, 81.92438, 82.95304, 83.853657, 84.637438, 85.315547, 85.909902, 86.418319, 86.882287, 87.275151, 87.604113, 87.904226, 88.152034, 88.380633, 88.574051, 88.744981, 88.895262, 89.031792, 89.143631, 89.240092, 89.320935, 89.402605, 89.472717, 89.527454, 89.598758, 89.644623, 89.689571, 89.720099, 89.763308, 89.801347, 89.833788, 89.859346, 89.882605, 89.906439, 89.940542, 89.942621, 89.975916, 89.994124, 90.010484, 90.058304, 90.05887, 90.057483, 90.071175, 90.089125};
double[] XWorking2 = new double[] {353, 354, 355, 356, 357, 358, 359, 360, 361, 362, 363, 364, 365, 366, 367, 368, 369, 370, 371, 372, 373, 374, 375, 376, 377, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, 389, 390, 391, 392, 393, 394, 395, 396, 397, 398, 399, 400, 401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, 414, 415, 416, 417, 418, 419, 420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453};
double[] YWorking2 = new double[] {-2.75759524458215E-05, 8.82744009754321E-06, 5.40915272797923E-05, 3.75544539582394E-05, 1.98865362625465E-05, 1.32638308596289E-05, 1.87948519794849E-05, 4.97612015229139E-05, 5.75202786636269E-05, 2.76631906945453E-05, 6.75159658656986E-05, 8.74759856273634E-05, 4.87199929134556E-05, 8.19705725644494E-05, 0.000131830246954611, 0.000107493398021457, 0.000134093566279347, 0.000154031639650182, 0.000200584243165729, 0.00024276768462815, 0.000292696555715455, 0.000370278806637968, 0.000507548959635451, 0.000696925108804524, 0.000848325774817128, 0.00101057506480742, 0.00128081439834991, 0.00170673955890091, 0.0021450925433506, 0.00274776437474421, 0.00355134787259316, 0.00447104532303219, 0.00557349898328843, 0.00690208613991011, 0.00845707959564937, 0.010241833150862, 0.012287329319398, 0.0145353736128952, 0.0169943597652841, 0.01963496316142, 0.0225242224152523, 0.0255717274284043, 0.0287432528361527, 0.0319952150013279, 0.0352825133923142, 0.0385402961856969, 0.0417595661343778, 0.0449535755736095, 0.0479951431227533, 0.0508119761601612, 0.0535037276547127, 0.0560799171731777, 0.0584931552699401, 0.0606595397433995, 0.0626391522587842, 0.0644290601093262, 0.0660031850685414, 0.0673912219231121, 0.0686259970138369, 0.069722172672137, 0.070612231250209, 0.0714604171728813, 0.0722775522216351, 0.0729267901245575, 0.0734496512690242, 0.0739106361218835, 0.0743721929136665, 0.0747896735359017, 0.0751280940518256, 0.0754099382754536, 0.0757062989689115, 0.0759867322633067, 0.0762673100829459, 0.0765239818239271, 0.0767863419756437, 0.0770477434166765, 0.0772557202155063, 0.0774793847905566, 0.077687548982008, 0.0779263076457929, 0.0781845847083027, 0.0783634165529564, 0.0784971903404137, 0.078626804476334, 0.078803424497818, 0.0789734275919643, 0.0791337594891459, 0.0792016018575865, 0.0792757610721576, 0.0794037729989908, 0.0794377290961222, 0.0795123238226576, 0.0795988794698434, 0.0796303502161205, 0.0797138160046204, 0.0798762316963929, 0.0799921074276644, 0.0801081854005132, 0.0802696642166181, 0.0804052511542033, 0.0805767834679051};
double[] XNotWorking = new double[] {420, 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, 434, 435, 436, 437, 438, 439, 440, 441, 442, 443, 444, 445, 446, 447, 448, 449, 450, 451, 452, 453, 454, 455, 456, 457, 458, 459, 460, 461, 462, 463, 464, 465, 466, 467, 468, 469, 470, 471, 472, 473, 474, 475, 476, 477, 478, 479, 480, 481, 482, 483, 484, 485, 486, 487, 488, 489, 490, 491, 492, 493, 494, 495, 496, 497, 498, 499, 500, 501, 502, 503, 504, 505, 506, 507, 508, 509, 510, 511, 512, 513, 514, 515, 516, 517, 518, 519, 520};
double[] YNotWorking = new double[] {3.0244883406976, 2.83295966596341, 2.66178772393115, 2.49536986054521, 2.35247588199072, 2.19841374699224, 2.06936371068534, 1.94447612701576, 1.81831456842034, 1.69769200302452, 1.58251936763242, 1.47521907858038, 1.35135675658379, 1.25090839300155, 1.14067148661186, 1.03486600913928, 0.940885459333528, 0.841598797944357, 0.757820203011102, 0.681046307555002, 0.604403396323645, 0.540025064033112, 0.478340422261197, 0.426974657986113, 0.380669495238637, 0.344752920421447, 0.308383765576425, 0.272432523054477, 0.257553728541763, 0.234062303492469, 0.223253270206317, 0.210696726465545, 0.202538266655753, 0.203759268701798, 0.198306955613973, 0.203629801021742, 0.212560116373918, 0.220336224892702, 0.232028290678333, 0.245959346305367, 0.259218171633184, 0.2777450536022, 0.299094726645395, 0.316459804412063, 0.336837522082181, 0.361473822363433, 0.380590389468502, 0.404441363493798, 0.429219686796428, 0.45268891421585, 0.475338033132888, 0.499594235650765, 0.522422547413789, 0.547349852935894, 0.572580202632931, 0.599658563792795, 0.627115230055263, 0.656437694235189, 0.683296196948674, 0.712500622293025, 0.746534480082464, 0.777474719140242, 0.812042697632694, 0.849618263659198, 0.888244565260653, 0.928551592890494, 0.970491986073818, 1.00849410234163, 1.04626154346002, 1.09104901197512, 1.12398319460137, 1.15910129489684, 1.1959450891667, 1.227494518776, 1.2569215613004, 1.28414396566287, 1.30865735634816, 1.33254240407815, 1.35255778946778, 1.37179321554218, 1.3880305032149, 1.40317688705949, 1.41412136847739, 1.42757192488658, 1.43922979047245, 1.45122451456189, 1.46340435861582, 1.47171825187438, 1.48166055117652, 1.49385044441323, 1.50595310332654, 1.51876982551541, 1.52990961265142, 1.54201881038538, 1.55440258816695, 1.56705411648325, 1.57994676788576, 1.59261608906482, 1.60416093621065, 1.61493837998244, 1.62469252781368};