Using R9 280X with modded bios and some overclocked GPU. v12 works fine. Tested over 2-3 days working without issuies.

With v12.1 only 1st intensity is most stable. With any other intensity miner after about 10 min starts to show 0 hashrates and 0% GPU load.
With 1st intensity miner works normal 20-30 min and then speed is 0 too. Miner restarts and so on.

Returning back to v12. It's stable for me.

Windows 10 Pro.
Tryed 15.12 drivers, disable overclocking. Nothing helps.
Any other miners works fine. PSU 60-70% load.