A decent number of Mac users are reporting system crashes after updating to macOS Catalina 10.15.4, which was released a few weeks ago. Users report that the crashes occur most often when the users are attempting large file transfers.
A SoftRAID forum post describes the issue as a bug and said it is working with Apple engineers on a fix or a workaround. SoftRAID says the issue extends to Apple-formatted disks:
There is a serious issue with 10.15.4.
It shows up in different scenarios, even on Apple disks but is more likely when there are lots of IO threads. We think it is a threading issue. So while SoftRAID volumes are hit the hardest (its now hard to copy more than 30GB of data at a time), all systems are impacted by this.
In our bug report to Apple, we used a method to reproduce the problem with ONLY Apple formatted disks. Takes longer to reproduce, but that is more likely to get a faster fix to the user base.
Meanwhile, other macOS 10.15.4 users report system crashes after waking their Mac from sleep. Affected systems go into a kernel panic and reboot to the Apple logo. Various users have reported such occurrences on the Apple Support Communities, MacRumors Forums, Reddit, and Twitter.
Last but not least, other users report that after updating their machines to macOS 10.15.4, they’re experiencing continuous spinning up and down of connected hard drives when the Mac is supposedly asleep.
We’ll keep you posted as we learn more.