Default i9505 Mobile Data randomly stopping


Sorry to ask but it's beginning to do my head in.
Recently I've used 3 different roms to test this and I'm having the same issue on all. My mobile data just randomly cuts out. Only usually after 20% battery but today it happened at 30%. And I have to reboot to get it back and if I'm less than 20% I have to charge it a bit first.

I've tried c-rom, pac-rom, imperium and currently trying chaos rom and still the same issue.

any ideas / suggestions would be greatly appreciated.

I always have mobile data on, on uk 3 network. If any more info is needed will do my best. Thank you

Serial Flasher .... Take that how you will