MsiInstallerExemptions is a sandbox setting in Sandboxie Ini available since v0.7.2 / 5.49.0.
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[DefaultBox]
MsiInstallerExemptions=y
Use the 'MsiInstallerExemptions=y' option to allow MSIServer to run with a sandboxed system token and apply other exceptions. This option may help with installing an MSI package.
Related Sandboxie Plus setting: Sandbox Options > Security Options > Security Hardening > Allow MSIServer to run with a sandboxed system token and apply other exceptions if required