When just opening the Fairphone 
for a card tray question, I kept struggling to unscrew any of its Torx screws with my multi-bit screwdriver set when applying the Torx T5 bit. The lime coloured screwdriver stub (that comes with the lanyard, cardholder or finger loop accessories) worked like a charm instead. My own T5 bit kept sliding off, and if the stub had not worked so efffortlessly, I would have thought the screws were already worn off.
However, I had a look at each screwdriver tip and at first sight, the T5 bit tip seemed slightly wider in diameter than the stub tip. For a try, I applied my set’s T4 instead and now it works just as snuggly as with the stub.
Has anyone else had this experience, too? Torx T4 better than Torx T5 for FP ?