Happens to us every job... What we found is we change the SSD to quickly sometimes.. and next thing it wont mount. Had us miffed for months! Finally figured out a solution... Which seems to work for us.
We turn of the SSD reader, then pull out the SSD... let it sit for about 1 minute, turn the reader back on wiat 10 seconds, them put the card back in.
For some reason it sort of needs to clear itself.
Hope this helps.