The issue you're having might indicate that the drive needs to be swapped.
If the SSD Toolbox reports errors on the "Data integrity" test or similar, it would be a good idea to contact Intel for an RMA request. Try backing up any valuable information on the SSD and have the drive on hand when calling. They will request the ISN#, PBA# and SA# from the drive sticker.
You can get in touch with them at 916-377- 7000, option 6.