Error in perturbations_solve with several NCDM species

[gaetanfacchinetti]

I am currently facing an issue while trying to run the unmodified version of CLASS (classy v3.2.3) with massive neutrinos and warm dark matter. A script with an example set of failing parameters is

import classy
cosmo = classy.Class()
cosmo.set({'output': 'mPk, vTk', 'h': 0.6766, 'YHe': 0.24500000476837158, 
'omega_b': 0.02242, 'A_s': 2.105209331337507e-09, 'n_s': 0.9665, 
'alpha_s': 0.0, 'P_k_max_h/Mpc': 10058.980279169373, 'reio_parametrization': 'reio_none', 
'z_pk': 1010, 'omega_cdm': 0.0, 'm_ncdm': '0.02,7507.499999999999', 
'N_ur': 0.00641, 'deg_ncdm': '3,1', 'N_ncdm': 2, 
'T_ncdm': '0.71611,0.08146910903562146', 'ncdm_fluid_approximation': '2,2'})
cosmo.compute()

which gives the following error message:

File classy.pyx:398, in classy.Class.compute()

CosmoComputationError: 

Error in Class: operator()(L:934) :error in perturbations_solve(ppr, pba, pth, ppt, index_md, index_ic, index_k, &pw);
=>perturbations_solve(L:3224) :error in generic_evolver(perturbations_derivs, interval_limit[index_interval], interval_limit[index_interval+1], ppw->pv->y, ppw->pv->used_in_sources, ppw->pv->pt_size, &ppaw, ppr->tol_perturbations_integration, ppr->smallest_allowed_variation, perturbations_timescale, ppr->perturbations_integration_stepsize, ppt->tau_sampling, tau_actual_size, perturbations_sources, perhaps_print_variables, ppt->error_message);
=>evolver_ndf15(L:466) :condition (absh <= hmin) is true; Step size too small: step:5.85188e-13, minimum:5.85188e-13, in interval: [0.371511:365.742]

In the vast majority of cases, the error does not show when removing 'z_pk' : 1010, however I need to compute the velocity transfer function at this redshift. I have tried testing other available solvers and changing perturbations_integration_stepsize without success. For the latter the value by default is 0.5 (far from 5.85188e-13 given in the error log) and decreasing it by half for instance did not change anything.

Any help would be greatly appreciated,
Thank you