Thanks everyone....

First thing I tried was resetting preferences to factory default.

Yes, I am trying it exclusively with CoyoteWT, or the included VST2 plugins (SynthFont, KV331, and sforzando) for testing purposes at the moment.

Also tried with VST2 plugins from Roland (Sound Canvas VA, SRX Plugins, etc), and Plogue engine stuff like sforzanodo/ARIA.

Rendering works again if I go with MME drivers, but then latency when trying to trigger sounds with the MIDI controller is insane. Perhaps I'll figure out how to get that tighter when I get more time to investigate this.

With the ASIO drivers everything about BIAB is snappy, responsive, and thus far seems solid as a rock (I've yet to crash or hang up the main app). I can play along with near zero latency. Everything sounds and works great! I just can't instant render and I'm not sure why. Getting a loopback to record in real time is easy enough, and I can also record in real time directly off the ASIO backend, or via Bidule plugin in an effect insert on the Mains. Just takes more time that way!

For now I've found a workaround. BIAB makes it very easy to swap between the MME and ASIO setup with a few clicks to change the entire settings profile. For now I'll just swap when I need to render, and swap back to work with the program in real time.

I'll keep trying things with ASIO in play and hopefully I can find the magic bullet that allows instant rendering there as well. Trying 16bit instead of 24bit might be my next move.

Windows 11, OmniPak