Happened again this morning. Powered the MD off and on again, tearing still present. Powered the tV off, tearing still present.
I reset all settings on the OSSC, left it on the default output and confirmed it had stopped. Applied the saved profile (which I had been using at the start of the session) and tearing had stopped.
EDIT: Separate session – tearing present at start, reset settings, applied same profile – no tearing.