Microsoft announce an issue and stated the Users should delay the new May 2019 build of Win 10 if they have attached USB storage or using SD cards.
https://www.extremetech.com/computi...ndows-update-on-pcs-with-usb-storage-sd-cards
Installation of the update may be blocked if present.
https://www.extremetech.com/computi...ndows-update-on-pcs-with-usb-storage-sd-cards
Installation of the update may be blocked if present.