II have a late 2014 iMac, many times tried to upgrade to high Sierra, but, OS apps keep freezing, forcing a hard restart.ing..nvram h-c; †; clan ins†all.

I have a late 2014 iMac, many times tried to upgrade to high Sierra, but, OS apps keep freezing, forcing a hard restart.

Works fine in Safe mode. I've tried everything..clean install; nvram -c; SMC reset..any advice would be appreciated..

Hardware Overview:

Model Name: iMac

Model Identifier: iMac15,1

Processor Name: Intel Core i5

Processor Speed: 3.5 GHz

Number of Processors: 1

Total Number of Cores: 4

L2 Cache (per Core): 256 KB

L3 Cache: 6 MB

Memory: 24 GB