I have exactly the same problem.

Styles are installed and are often working fine, but sometimes, an Error 256 comes up, regardless of whether I sub a real track or not.

I have discovered that I can usually regenerate a single track by right clicking on the track itself > track actions > regenerate.
Same for utility tracks.


But this trick doesn't work for drum tracks. When the drums remain silent after happily counting the band in, I need to close BIAB and restart it again, which seems to fix it.

This error is a bit of a nuisance, and it also happens when picking styles and choosing to play back the first 4 bars of the arrangement. Quite often, tracks will remain silent, or a style may be reduced to a lonely shaker.

I also use the sour note fix quite often, which I am very grateful for. But maybe it's got something to do with that?
During a support chat, it was suggested that perhaps some of my style set files might be corrupt and that the error would appear if the generation was calling for a particular pattern variation... ?