Recently any bow I have with soul trap has stopped working correctly. If I kill the target on the first shot, then a gem does not get filled. If I use the same bow, or any other weapon, after the first hit, then it does work. It's like the soul trap spell doesn't take immediate effect anymore. I haven't tried this with a sword yet.
I have installed a few mods, so I guess that's where the problem is, but I thought I ask to see if anyone had this problem and fixed it.
I can probably make due for the rest of my game on the gems I already have and just purchasing them I guess.