SM-T530 Lollipop update problems

Hey guys,

My wifes Tab 4 recently did the OTA update to Lollipop (5.0.1) and has been having a problem ever since. After being in use for a few minutes after the update it suddenly locked up and rebooted itself. Thought nothing of it at first, but then it did it again, and now randomly reboots all the time, sometimes after only a minute of use. I've tried clearing the cache partition and factory reset, neither gave any improvement. Then i figured maybe the OTA download was the probblem so i flashed it back to Kitkat using Odin and all worked fine again for a few days. I turned off the OTA update checke and she was perfectly happy with it again.......

......until it downloaded the update all over again.

Before allowing it to update again i connected it to the PC and did the update via Kies instead. All seemed to be fine for about 5 minutes and then started rebooting. Again, cleared cache and factory reset. Again no improvement.

Then tried flashing the update via Odin again. Still no improvement.

I'm drawing a blank on this one. I've tried everything I can think of and still not been able to solve this one. The only thing i've been able to figure out so far is that for whatever reason it doesn'T randomly reboot if its connected to the PC via USB...............

Anyone got any ideas how to sort this?? Samsung have offered to take it in for repair and I'Ve been offered a refund from the retailer, but I'd rather avoid those options if possible.

Thanks!