Don’t know why but it seems to me the SanDisk product reliability has taken a sharp nosedive. I install decentralised digital video surveillance with micro sd cards as storage. Previous 16, 32gb were much more reliable. Currently 50% of my recent micro sd cards won’t even format complete out of the box . Another 25% fail within 30 days. That leaves on 25% that really work. Things that make you go hmmmmmm.