Perfectly align multiple items

Okay, so. I'm transitioning completely into reaper. In my last saw I tracked vocals over a premixed instrumental, not synced to metronome. No big deal as I moved everything together on time with the click afterwards and it was all on time. So now the beatmaker sent me the stems for the beat. I've manually synced the stems on the grid and extremely close to the unmixed place holder track, probably more than close enough. However I can still hear some slight phase when playing the stems and the pre mixed beat together. Any good methods for getting them perfectly in sync?

Might be a good idea to acquaint yourself to Reaper's Stretch Markers! You could also take a look in the Lua scripts other members have posted, one of them looks particularly up your alley for this case:

It's all non-destructive.

Also, the below script is very handy too for a bit of an automated way of doing it. :) Not finished yet but getting there. .

Bump Would like to know if this stretches the audio to fit other tracks, or if this just moves them closer into position. These are all the stems that were used in the premixed beat, i just want to align them to it with perfect sync. Not morph the audio into the premixed beats position.

The script by mpl analyzes a reference track and aligns the other tracks accordingly. No grid involved (you might use the click track though).