A SOLUTION !!! - A month or so ago I posted to this forum the fact that my 2019 iMac 27” also crashed during sleep. It was more like it had done a restart as I would find it sitting at the Account/Password prompt. I THINK I KNOW WHAT IS CAUSING THIS PROBLEM, IN MY CASE. My iMac has a 2 TB internal SSD and a 2 TB external SSD (named “Photos Library”), the latter used for my extensive collection of photographs. I recently purchased a Mac Studio and a Studio Display, the latter arriving on April 12. I partitioned the Studio’s 4 TB drive into two 2 TB volumes, the second of which I also named “Photos Library”. I used Migration Assistant to copy the apps and files from the iMac to the Studio’s boot volume. I then did a Finder copy of the “Photos Library” files from the external SSD to the “Photos Library” volume on the Studio. While doing all of the usual adjustments to the new Studio after migration, I put it to sleep quite a few times when something else had my attention. To my dismay, THE STUDIO ALSO CRASHED! A light bulb went on in my head when I remembered that the Photos app processes the current Photos data file, “FAMILY.photoslibrary” in this case, when the computer is sleeping, assigning people’s names to their likeness in images and probably doing other housekeeping chores at the same time. What if Photos encounters an error during this processing that is not being trapped and handled gracefully? That could cause a crash. I have been testing this hypotheses ever since. On the Studio, I put the Photos data files in the Trash, so Photos' background routines will not find them and it will do nothing. On the iMac, I simply did not hook the external 2 TB “Photos Library” drive back on the computer. I have had both computers running when I am not using them, including all night, and have had NO CRASHES! I’ll report here if one of these systems does crash, but I think this might be the problem.