Does anyone else have to forcible pull the slide off almost like its stuck or has some resistance?

I found the trick of putting the slide back on by pressing down the striker safety thingy in the frame...

Haven’t had a chance to shoot it yet so it may just be really tight

Got grease?

When you field stripped your new pistol, did you clean and lubricate it?

Yeah cleaned and lubed...it doesn’t seem to be the rails seemed like a hang up inside somewhere

My normal 365 is rather difficult to take down and put back together as well. I've only put 200 rounds through it so far, hoping it will "break in" as time continues.

The take-down lever and slide lock both need
to be held down (they work together) to
replace the slide on both the P365 and the
XL model.
This was told to me by a Sig rep early on.
i knew something was stopping the slide from
going all the way back.
Poli Viejo

Yes, the takedown lever should be pushed forward a little when you move the slide. As in it is already in the vertical position and you push the bottom toward the muzzle. Shouldn't need to really muscle anything.