Sporadic "Attempting system restart...MACH Reboot"

[macOS XP]

Hi everyone!

I have recently encountered an issue with my MacBook Pro Early 2015, which would sometimes not boot anymore, the progress bar stopping shortly after the beginning. When pressing cmd + v during startup, it stops the startup sequence at the message "Attempting system restart...MACH Reboot". I read about this error in some forums, but they seem to only occur on hackintoshes. Some time later it starts up and works fine.

What I have already done:
- The ssd is not at fault. It was replaced with an ssd which already had Catalina installed and worked perfectly for over a month in another MacBook Pro. Same issue after a few days again.

I would really appreciate any help. Thanks very much!

 

[HDFan]

The ssd is not at fault. It was replaced with an ssd which already had Catalina installed and worked perfectly for over a month in another MacBook Pro. Same issue after a few days again.

Did the system ever work properly after replacing the SSD?

 

[macOS XP]

Yes, and it also did before with the old ssd. It is just sporadically having this issue. Also, once I wasn't able to log in after was in sleep. It just timed out and after a few days it startet up again. But when it is working, even heavy workloads are no problem, like exporting a project in iMovie.

 

[macOS XP]

So I tried some things today, none of which solved the problem. I unplugged literally everything on the inside, except for the keyboard which is obviously necessary for turning the MacBook on, and even tried booting from a usb with Catalina installed, before and after removing the ssd. I also tried just running on the charger, with the battery disconnected, no success either. Resetting the NVRAM and SMC had no effect at all.

I really don't know what to do anymore, does anybody have suggestions?

I also attached a better photo of the POST messages.