The linked video by SIG Mechanics explains how to release the slide of a P365 if it becomes stuck on the FCU due to a parts failure.

https://www.youtube.com/watch?v=jDOyS6Wa_6M

If you are not familiar with his videos about the P320 and P365, they provide excellent advice and demonstrations about the mechanical operations of the pistols.

A few weeks ago, I had a failure of RSA (the last coil on the RSA jumped over the adjacent coil) which completely locked up my slide. Since I couldn’t completely lock back the slide and disengage the takedown lever, my only option was to rip the slide, along with the FCU off the frame, manhandled it.

I have a spare niw RSA, installed it and immediately I couldn’t do a takedown. The slide was stuck like it the video. After a 30 minutes of messing with it. I finally figured out a way.

With my left palm over the slide, I retract the slide about 1/2” or so. While hold the slide back at this position, With my right thumb over the take down lever, I started working the lever back and forth about 10 times. You should feel the tension on the lever working against the RSA. After this, the slide came right off.