This means that at the given parameters it was unable to solve all of the way. Given the dtmin, this looks to be because it’s using Float32 numbers. Float32 is not going to be as capable of handling numerically difficult cases as Float64, so I’d recommend trying Float64 and seeing that’s fine.
Any simulation can go unstable depending on the parameters. Optimisers.AdamW is a stochastic optimizer, so you’ll get different parameters each time.