Here's a quick test build of VOPL3 that changes the renderer program to stop streaming any audio when the Adlib is idle. This breaks the status of the Renderer in the system tray app a bit, but you should be able to see if that prevents disk corruption while not actively playing audio.

I have also prepared a version of VOPL3 that does that. The installer won't overwrite the existing vopl3.ini file, but it will copy next to it the new template. Either overwrite it manually, or just add to your existing .ini file:
idleclose=5
This will close the audio stream after 5 seconds of FM silence. Set it to 0 for previous behaviour.

i've had this running again with idleclose=10 and all seems well. i installed the v0.20b21 george breese pci latency patch on top of the 4in1 v4.35 drivers.

the only suggestion i'd have at this point is to make the installer more granular in regard to choosing between fm and mpu401 port trapping. i have use cases for the current options of fm-only and fm + mpu401 for my laptop with a wretched ess maestro 2e or my wavetable isa cards without a ymf262 (or even a hardware opl3). by far my biggest use case is mpu401-only for use with windows softsynths and virtual midi loopback cables (accomplished prior with vdmsound granularity). it would be nice to have this option and be able to banish the cludge that is vdmsound 9x entirely.

I considered doing that when adding MPU-401 bridge support but never implemented it as I though it would be a bit silly having a tool named VOPL3 that can be configured to only do the MPU-401 port trapping and redirection. I can see how it can be useful though. I'll add that in the next release, which will include closing the audio stream when the OPL3 engine is idle, and a couple of other things.