mac mini 2011

Best regards and safe passage to everyone.

Bought a manufacturer refurbished Mac mini 2011 with 10.13 installed. Connected to Asus 27/8Q with HDMI.

Problem : Booting appears normal with a clear Apple logo and progress bar. Then screen is filled with colored dots and squares. However when booting into Safe Mode, the screen has the dots until I sign in, then a normal 1080p screen shows. I have ordered a mini-displayport to DisplayPort cable to see if that makes a difference.

Anyone with a similar problem ?

My take is that one of the kexts, plists or caches that is NOT loaded in safe mode is causing the problem. But there's a lot of them... Is there a list that shows what is loaded and what is not ?

Finally, would anyone like to venture a guess on which kext, plist, or cache I should try to delete first ?

Thanks