Don’t really know where to start

I’ve been a avid viewer for some time and attempted a few things.

However I’ve come unstuck with my sons PS4 and can’t seem to find a straight answer anywhere.

I stripped it down and cleaned it thoroughly, reapplied the ‘Right Amount’ of Thermal Paste, and put back together.

Whilst I was doing this I thought I’d put a new SSD in to replace the old HDD, I’ve done the process years ago when putting a bigger HDD in and had no problems.

Now I get either SU-42118-6 code or I’m stuck on 99% after initialisation, left it for 4 hours and nothing.

One thing I did notice is the Blu Ray Ribbon was damaged, would that cause the issue? Also would that stop it accepting Discs?

I would like to point out that if I put the original HDD back in it boots up and plays fine.

Also new SSD works in the PC once formatted and I’ve filled it to 60% to test it.

Any advice would be gratefully appreciated.

A damaged or unpluged bd ribbon cable can cause a SU-42118-6 error massage.
At an update/recovery all components of the console are checked and if the bd is not responding correct, the update get stucked. I guess at the next update with the old HDD the same error will appear.

I would check with a multimeter in continuity mode if the damage on the ribbon has caused broken lines.
If so I would replace the ribbon cable.

Perfect, replaced cable and worked first time, thanks for you time.