So I have been playing through the base game, Cryptic Passage and up to this point through the excellent mod "Death Wish" without problems, but here I seem to have stumbled over one that is preventing me from entering the first set of secret levels in Episode 3 of Death Wish (Spoiler ahead).

This jump doesn't work.
I have the current version of Fresh Supply and loaded the current version of Death Wish properly as an addon:
https://www.youtube.com/watch?v=Isv_GqDLM_c&t=12m15s
I reach the gate easily, but Caleb won't stand on the ledge, just slip down as if it would be a flat wall.
This is unfortunate, because it leads to the entrance to bonus levels for which I already found the key.

Did anyone make it or did you use the no-clipping cheat?
Am I missing something?

Probably not, in as much as it's likely some incompatibility/bug/quirk between Death Wish and Fresh Supply, especially since pagb666 seems to have no issue in the GDX port.

I already got a reply from the maker: Huh, I guess the bigger hitbox in Fresh Supply makes the game overall even harder, enemies should land more hits due to it as well.

I'm not one of the perpetually angry folk when it comes to Fresh Supply but the fact that this is even a thing that was left "as is" in it is mystifying beyond all belief.