Are you using the latest version of Phoenix miner?
Version 5.4c: https://bitcointalk.org/index.php?topic=2647654.0

Check the riser cable if you're using one

And the most important, leave at stock settings, 100% power limit, no memory or core clock overclock, and let run for a day
Maybe your card doesn't handle overclock like before

Alternative: you can use Nicehash, and the nicehash miner "excavator", this app will restart miner if some issue happen