240G having some issues

My SSD is sometimes not showing up in the BIOS and sometimes it does but is not set as the default boot drive. When it does boot into windows it is extremely laggy and will sometimes stop responding all together. Have ran a scan disk to no avail. If I mount the drive via a USB 3 dongle it will prompt me that there are issues that need to be fixed however this process takes a long time and appears to not be progressing at all. I can however mount the drive and navigate through the files. Doing this the drive seems to respond very quickly - i.e. no lag or stall.

My SMART results can be found here: https://dl.dropboxusercontent.com/u/12255470/Smart%20Test.CSV 

Even though there are Passes in the test the BB results look bad and failed.

Any ideas / help would be appreciated

The reported uncorrectable errors you have are extremely high. That said you can try secure erasing the SSD. If the issue continue contact sandisk support and check warranty status.