Assertion: 'inchannels <= mMixMatrixCurrent.numin()'

I receive this error in the debug callback

assertion: 'inchannels <= mMixMatrixCurrent.numin()' failed

File and line info
Trace : < assert c:\jk\workspace\Build__1.10__API_Win\lowlevel_api\src\fmod_dsp_connectioni.cpp:575]

What does it mean and how can it be resolved?

You are seeing an internal consistency check fail, could you provide a way to reproduce it?
Once we know the cause we will be better positioned to recommend workarounds or action a fix.