I’m not sure if this issue was brought up before, but I’ve noticed that upgraded thrusters don’t work for me if I join an ongoing warzone match
Sometimes they dont work for me at all same with the other armor mods.
This has been happening since the GoM update. JIP Req levels are the same way from time to time and that was supposed to be one of the update fixes
You can check this thread for a temporary workaround until the issue is resolved 
Warzone armor mod bug