Your posting is ambiguous
Which update? OBS or Windows?
And which audio stops?
It depends on what OBS is recording (ie General Desktop audio, or specific audio sources?) and what you muted?
if you are recording Desktop Audio and you Mute Desktop Audio, I'd expect OBS to record empty audio... but I could also see that Desktop Audio sources are still going, and you are only trying to Mute Speaker Output? is that correct? In which case, you could have an audio sub-system driver update, an OS update, or an OBS update changing where/how the OBS audio hook connects to.
So my advice would be to provide some clarity on your specific setup for more specific recommendations for troubleshooting, then follow the forum pinned post on posting a log when asking for assistance
