jope @juliansader that it was.
BR_GetMouseCursorContext_MIDI retval value #783
https://github.com/Jeff0S/sws/issues/783
The problem with this fix is now...
if you would do it right (docu) like example this
_, _, _, ccLane, ccLaneVal, _ = reaper.BR_GetMouseCursorContext_MIDI()
this would break your scripts with the last stable 2.8.3
and if you would do it like this to avoid the issue within 2.8.3
_, _, ccLane, ccLaneVal, _ = reaper.BR_GetMouseCursorContext_MIDI()
this would not be like within docu and break the SWS versions which include the fix...
normally 2.8.7 should be the last stable SWS at sws-extension.org and not 2.8.3 but we all know......