I’ve had similar problems–no trouble training for a few months, updated to 0.3.0 and started training some new models which started to go wildly and unexpectedly unstable; the slight changes to my code made it hard to pin it on anything in particular. It disappeared for a while as I was training smaller models, but I’ve been running a ResNext50 on ImageNet and it’s had crazy unexpected up-and-downs (like, randomly jumping from 20% top-1 error to 60% top-1 val error, then going back down slowly, then randomly jumping up to 99% val error). I’m downgrading to 0.2.0 and running it again, will report back in a few days if it goes unstable or not.