Late 2015 iMac crashes with MCA Error when playing video or music.

Hi everyone,

I would appreciate any inputs from anyone.

I bought a used late 2015 i7 5k iMac for $300 cad last year

Symptoms include:

• Flickering/split screen
• Choppy audio and video freezes during media playback
• Works fine in Safe Mode
• Can run short 1080p video for a minute or two, then crashes

I’ve ruled out SSD or RAM issues. Has anyone seen similar MCA/CATERR errors on this model? Could this indicate GPU/logic board failure, or something else? Any advice is appreciated.

I’m having repeated crashes on my Late‑2015 27″ iMac (4.0 GHz Quad-Core i7, Radeon R9 M390 2 GB, 16 GB RAM). After replacing the SSD, the system runs fine for basic tasks like browsing or email, but crashes when playing media with the following error:

Diagnostics Information (past 60 days):

    2026-02-16 17:07:59 Kernel Panic (2 times)

        First occurrence: 2026-02-16 14:16:15

        Details:

            *** MCA Error Report ***

            CPU Machine Check Architecture Error Dump (CPU: Intel(R) Core(TM) i7-6

            700K CPU @ 4.00GHz, CPUID: 0x506E3)\r

            CATERR detected! No MCA data found.\r

    2026-02-16 16:44:24 Kernel Panic

        Details:

            panic(cpu 2 caller 0xffffff801bf8099f): userspace watchdog timeout: no

             successful checkins from WindowServer in 120 seconds

            Panicked task 0xffffff8b89d713b0: 3 threads: pid 96: watchdogd