Flash drives are tricky  some  are poor quality.

Some are good.  

I prefer  usb sticks  for my smos.

I prefer  small ssds for windows.

Here are some sticks that work for smos/linux


https://www.amazon.com/gp/product/B00KYK2AKO/ref=oh_aui_detailpage_o03_s00?


and these are nice  but I just started using these


https://www.neweggbusiness.com/product/product.aspx?item=9b-20-147-454



small and so far so good.