Wave scene? I don't think I ever got such a thing. I've never flirted with Gale or Astarion, but when the tiefling party started both invited me for some hot sex and I had to turn them down as I was going for Lae'zel.
I have read something like that. In my case he just cheered PC and SH. Funny that only Astarion had yellow sign above his head. When I saw where it's going, I just simply reloaded and went straight to Shadowheart before interacting with others. This locked other romances. Maybe they patched Gale's triggers because I had no weave scene (kept him at distance, artifact feeding was enough from my side). PC is supposed to kiss Gale during weave scene or something. Not sure about sex after battle but Gale may give also awkward sex proposition post tielfling-camp scene, he ignores the fact PC has romanced someone else. Luckily, I have missed this unpleasantness (didn't trigger; weave scene required).
