This U-tuber identifies the problem with the out-of-spec disconnector lever (on trigger bar) and improper reassembly technique (supposed to lock the slide back, push the slide stop up first, push the release lever forward). Per the U-tuber reassembling it like glock may result in only partial sear contact.
https://youtu.be/utGmYit8YZA?si=V8npFonyZJkj065t
The above U-toober was inspired by this video by
Three P20's in a Trenchcoat:
https://youtu.be/KuTxhHZ0uiA?si=dvRSGDSYabvsv3wB
I've no opinion as I've never seen, handled or examined a Sig P320.