Years back, I had problems using Torx (read: cheaper star bits) in bolts that should have been T40 or T45. I thought the solution was a TPlus40 bit and when hammered in, they worked well, I thought.
Ultimately, the solution was really to get quality Torx bits that actually fit the bolt properly. Apex was carried at Harry Epstein and I picked up several.
I also noticed the mfgr. changed their bolts so cheaper bits worked better, but so did quality bits.
Lesson learned: try a few different tools if the one that should fit, doesn't. Also, re-evaluate periodically, mid-year changes can hurt, or help.