I'm stuck on the quest Blindingly Obvious trying to sneak up on Philipa but for some reason Geralt refuses to jump over this gap in the stairs and just keeps dodging. Is this some kind of glitch or am I doing something wrong?

yes and there is no official fix for this anywhere, just a mod someone made, i may have to try it since the developers aren't showing any interest in a progression bug

The mod does work, it's how I was able to complete the game. Very frustrating though, that the Devs have ignored this.

Yes i did use that mod and got passed that part so i could finish the game, shortly after at a dock ppl were floating while walking and heads were floating around, not sure if that was related to the mod but it was funny lol

I managed to jump across, although it wasn't easy, as Geralt cannot into jumps while he is in combat. Took me several attempts. Pretty annoying thing, must admit. Two of following quests have even more annoying bugs.