Sorry no logs or screens for this. I guess a video would help. Didn't find it in the Bugtracker but not sure exactly how to post about this there.
How to reproduce in Alternative HUD (haven't tried others much):
1. You start a new tactical mission.
2. Pick a soldier.
3. Move soldier a little, then set react fire to burst or full auto or similar and keep moving past where they should really stop for react fire saving TUs.
4. The very lowest react fire setting Snap Shot or similar seems to work better.
5. If the very first thing you do before moving or having a soldier do anything in a turn is set the react fire, then the bug doesn't appear as consistently.
In other news setting react fire settings are a bit of a p.i.t.a. in the Alternative HUD - which is my favourite HUD for a few other reasons. Going through and setting react fire only to have people completely disregard saving the required TUs is a ...downer.