[Steve_U1S]

After searching and finding some posts that gave some insight and came close to answering this, I'm looking for opinions/advice from anyone who has had similar/same issues and might know the source of this:

This is a KSC G23F HW (Japanese), just a couple of months old now, and I've just installed a metal slide/Guarder recoil spring kit (Thanks MadMax/ASC Armoury), and went from duster to propane. (I have the upgrade hammer spring, but have yet to tackle that, but I haven't found a connection to suggest it might be the issue here.)

The symptom that's cropped up is this: it appears that the blowback nozzle is sticking forward during recoil.
The thing I do notice is that it's more apt to happen when the mag is in; when it's not, it does pull back the majority - but definitely not all - of the time.

Things to consder; the slide comes with a set of what seem to be slightly beefier than stock springs to bring the blowback chamber back to position, which I did install. They aren't mangled, causing binding. I actually took things back apart and did a lot of de-burring and slight oil coating of the metal slide where I could feel there was some binding of moving parts - the area where the blowback chamber is seated is one of those. The chamber is also lubed so that it moves completely freely.
I did this de-burring/lubing of the slide for the outer barrel to reduce friction for easiest action of the new metal slide possible.
I stripped it back down and pulled the springs out, and gave them a bit of a stretch to offer more strength to pull the nozzle back (that was a trick, getting those to go in without getting mangled); didn't do the trick.

I have read about some similar springs being put in there (lighter springs, for one) and will keep that in mind, but in all, it just seems there's some binding that I need to address, but just can't find.

Light coating of silicon also applied, excess removed. No love.
I thought it might be the tail end of the outer barrel - nicely machined, so rather sharp-edged - catching the nozzle during the tilt, before the chamber pulled back, so I did some deburring/polishing - no dice there, either.
As a test, I popped the original plastic outer barrel in and did some test racking of the slide; it still stuck in the same fashion.

This condition is causing misfires and, it would seem, a lot of lost propane. I'd get a few good solid shots, then a dud - and I'd pull back the slide and see the nozzle sticking, and no round ready.

One other thing; before I knew to just field-strip and finger adjust, I used the hop-up adjust tool included and left some dings to the loading ramp, which I have since smoothed away with micro-filing and polishing - again, this shouldn't be involved, but thought I'd mention it.

Also of note; the pistol was firing fine before the upgrade process (and almost makes me reconsider leaving the metal upper parts on there...)

If I've missed giving any relevant details, let me know.
Otherwise, any suggestions/advice appreciated.
Thanks.