Yeah, I’m not having any issues with hard L/R pans using my mid/side setup… but I just checked in instrument fx. Don’t see why it wouldn’t be different in track sends, tho.
try using this doofer for your side extraction and see if it makes a difference for you
UTIL - SIDE isolation.xrdp (3.6 KB)
yes, this is how I use it, but in individual instrument fx chains. If you’re ok w rendering to samples, this might be the ticket. Although I could imagine wanting to M/S process the whole mix, too… I’ve just never done that yet 
I really wish we had multiple fx chain available in doofers, would make it super simple to drop M/S processing into any track, regardless of sample vs vst sound source
@taktik is there any chance of this functionality (and ideally, modulation input/output as well) being added to doofers in a future release? Would be a HUGE power-up for renoise, and would rival Ableton’s fx racks, and to some extent bitwig’s grid. Just my unasked-for entitled opinion, lol
here’s a link to the whole M/S instrument fx chain setup: Native Mid / Side Processing - #32 by slujr