Dolan Track Champion Track Ends

there are some allen keys that are 5 sided rather than the traditional 6 sided
could that be the issue ?

Good idea, but definitely six. Thanks!

Dolan are a UK company, ring em and ask.

Could your 2.5mm or 3/32" allen keys be worn? Sizes that small don't stand up to use and abuse very well.

I bought a (big) set of decent allen keys brand new for this build, so no, but it's a sound idea. Thanks for your help.

I think I'm going to ring them now!

Thanks to everyone for their input.