I have personally gone through each campaign from start to finish at least 3 times, and have swapped between with no problems. Are you certain there isn't a mod that is somehow conflicting with the levels?

How did you get past ep1_c17_02a weapon swap?

Ah, yes, that one's a weird one. Yeah for some reason Alyx stops moving after her dialogue. To fix this I just collide into her to move her in front of the shotguns and she'll pick one up. I don't know why this happens; the shelf the shotguns are sitting on probably have some weird collisions that gmod is having a problem with.

OH, another way of doing this is to use the "drive prop" feature by floating the shotgun out of the shelf. Just be sure to release the prop BEFORE she plays her pickup animation otherwise the sequence breaks. This is especially useful if you're using HL2 weapon model replacements that have different worldmodel collisions, like the MMod Redux one I use.

Just tried it again, and this time she automatically walked up and picked up a shotgun by herself without my intervention (this time I had the MMod Redux replacements disabled). No idea why this happens; guess it's just Gmod being Gmod.

GG thanks

Ok, just figured it out: the problem is the game's attempts at making Alyx follow the player. After she says her dialogue, walking up and touching the combine barrier will allow her to get close enough to the shelf to swap out for the shotgun.

This doesn't work with the aforementioned MMod Redux replacement because of the worldmodel collision changes, but the "drive prop" is a workaround fix for it though!

Also, no you're not. This is a very valid problem that can be easily mistaken as an animation issue. Honestly though, thanks for bringing this up, so that I know whether my addon broke something!

Yeah although I've been trying to debug this issue with my version of this addon for the last five years, but thank you

I always thought it was a capability that gmod never had ported from the episodes or something

I'm pinning this since it covers a potential confusion point in the episode 1 campaign (feel free to change the title, btw).

Gotcha