Hello danielpo123,
Based on the SSD specifications we can confirm that is capable to work in either a SATA 2 or SATA 3 interface due to the fact that is backwards compatible.
Now, the issues being reported seems to be a compatibility issues between the SATA controllers integrated in your MacBook Pro not letting the SSD to run as if it were a SATA 2 device.
Our recommendation is contact Apple* to see if there is a firmware update for your unit and check if the issue is resolved. Also, we would encourage you to have this SSD tested into another unit that fully supports SATA2 or SATA3 devices to check the SSD functionality.
Regards,