Re: Good question!
"Whats the wafer thin mint that finally causes windows to explode?"
20H2 update in my case. Well, it nearly caused me to explode last weekend. I've got a crappy 2GB/32GB laptop with W10. "Update to 20H2?" OK. "I need more disk space, please insert a USB drive." OK. Hours later, install fails.
"Update to 20H2?" Retry. Hours later, install fails.
Dig about. Somewhere there is a log of updates. Mystery eight-digit error code. Look online.
"This error code appears if you try to update using a FAT32-formatted USB drive. Use an NTFS-formatted drive instead."
Seriously? No check when I insert the USB drive, to say: "This one isn't suitable, please use another or reformat this one"? Just, "USB drive found. Should I use this one."?
FFS.