Flashdrive stuck at 200 MB
You can try force format using terminal


Enter this in the terminal "diskutil list"
Then a list of devices will be shown.
"diskutil eraseDisk JHFS+ diskname diskidentifier" replace disk name with device to formatted.
In the command above, change “JHFS+” to “HFS+” if you want a volume that is not journalled. Change “diskname” to the new name you want for the disk, and replace “diskidentifier” to the Disk Identifier obtained from Disk Utility. If you want to reformat, replace eraseDisk with reformat and delete the “JHFS+” and “diskname” parts of the command.


You can try the above steps. Hope this will help.