i very, very rarely encounter bugs with Charlatan [if ever], and i've realised a vst i thought was simply imcompatible with openmpt the other day was actually being affected by whatever is causing this, which is why i'm reporting it here - i would assume it was an issue with the plugin otherwise.

for a while i could get around it by saving and reloading before it inevitably struck again, but this file seems to reset every time.