Why do I get miner crashing every 24 hours or so with error 77 on random GPU when I run all 8 cards with 1 instance(1 window) of miner + some invalid shares(3-4 per 1500 or 1 day), but if I run each card with separate instance of miner(8 windows) I don't get any crashes for 2 weeks(and I simply didn't mine longer that until I close miner myself) and may be 1-2 invalid share during that time from all cards combined?