Chosen Solution
Hi Guys, I am a repair technician and i have an iMac 2017 4K 21.5”. It freezes a lot, like every-time i use it starts lagging, every 3-5 seconds it gets freeze for 1 second and mouse pointer gets freeze to one position and after a second it find it somewhere else. I have replaced the Main Logic Board and also tried checking with another Known Good HDD, this is happening in recovery mode also and also when i try to do the internet recovery mode. I am not really able to understand whats the problem.
You could have either a software level issue or your system is running in Safe mode as a sensor is telling SMC to go into this condition. I would run the built-in diagnostics to see if anything shows up their. Reboot the system and hold the D key. If an error pops tell us what is said. If this is a software issue you could have malware or you have some app consuming the processor threads. Open Activity Monitor and see what the top %CPU load is by clicking on that column.
