usb thumb drive problem?

(Fedora-30) After doing my weekly incremental back-up, I noticed too much of a drop in unused space on my USB thumbdrive was unusually low. When I look inside the end that goes into the port, it's black, which I believe means it's a USB-2 stick.  It's 16GB. I tried "Disk Usage Analyzer".  Nice graphs, but no indication of problems.  This is true both when run as root and when run as a common user. I tried "Gnome Disks". 1. When I click the part of the graph marked "Filesystem Partition 1 16 GB FAT", it shows beneath the display: Size 16 GB - 9.9 GB free (38.0% full) Device /dev/sdb1 UUID 3900-1AD5 Partition Type W95 FAT32 (LBA) Contents FAT (32-bit version) - Mounted at /run/media/[etc] 2. At the bottom of the display, I click the two gears, and select "Check Filesystem...".  After confirming, after a couple of seconds, I get a pop-up saying Filesystem damaged Filesystem vfat on  needs repairing. Results are the same when run as a common user as when run as root. GSmartControl seems to not know what to do with this thumbdrive. That's it.  Are there any other tools that can tell me more, like how much space is unusable, or how many blocks(?) are damaged?  If I ask "Gnome Disks" to try to repair the filesystem, how much risk is there of losing data?  Is this thumbdrive on its deathbed? thanks, Bill.