Mac crashes upon going to sleep

My 2019 iMac 27” running Mojave 10.14.6 with security update 2020-007 installed has recently started crashing every single time it goes to sleep or is put to sleep. These crashes started happening 10 to 14 days after installing the last security update (14 Dec), and I’ve installed no other software in the meantime.

I’ve tried putting the Mac to sleep after a safe reboot and after disconnecting all peripherals—still crashed. I’ve run Apple’s diagnostics with no resulting error codes.

There are massive amounts of discussions regarding similar problems but they are either generally centered around Catalina, which I’ve never installed, or T2 Macs, which my model is not.

I’d greatly appreciate any insight or advice regarding this problem! Thanks.

Not saying this will help but since you didn’t mention it, have you tried an SMC reset?


Didn’t mention it because I forgot about it but since you reminded me, I tried it and it seemed to work! No more crashing upon sleep (at this point). It also seems to have resolved another problem I didn’t mention, a USB-C connected hard drive array which upon an earlier crash refused to show up on the Desktop or in Disk Utility, now appears again.

So…thank you very much, Simon!


Glad to hear that did the trick. :slight_smile: