Failed Disk repair Warning invalid internal flag

Neither! You have a failing HD SATA cable as explained here Your Hard Drive Cable Is A Ticking Time Bomb Follow this guide to take it out and apply a strip of electricians tape on the upper case when the cable crosses over. You’ll also want to replace as well! MacBook Pro 15" Unibody (Mid 2012) Hard Drive Cable Here’s the guide to put it in MacBook Pro 15" Unibody Mid 2012 Hard Drive/IR Sensor Cable Replacement

Even stick you want to be care you don’t damage the cable as many people damage it in the process of putting it in. You don’t want to crease the cable as that will damage the thin foil wires in the cable. I use a old BIC pen Ink straw to help form the bends as I don’t want the radius any tighter.

Then you want to back up your data off the drive using TimeMachine, Reformat the drive and then install a fresh OS onto the drive at the end of the install process you’ll be asked if you have a timeMachine backup to restore your stuff back on (Migration Assistant).