Some say it is Stem's achievement notification and that turning off the overlay stops it. Some say it is when you level up in a skill.but this was not happening. I can't find any reliable explanation of what this is. At its worst it occurred 22 times in one second. On one occasion where the game ran for quarter of an hour I lost count at 600 repetitions of this line of script.
This occurs all the way through each and every log and is almost always right at the end of the log before the crash. Running papyrus logs, one thing sticks out like a sore thumb but I can't find out how to eliminate it. Nothing worked, except to reduce the frequency of the crashes as I described in the first paragraph. I'm having no problem with the computer on anything other than Skyrim. I ran Rkill and Malwarebytes anti malware, then malwarebytes anti rootkit. These have been installed for a few months and have never given a problem before. I have the legendary edition patch, dragon soul relinquishment and a mod to give longer duration of crafting potions. Before I did that, they were every 5 minutes or so. I get them now about every half hour but that's only because I've turned off all autosave options, disabled cloud synch and disabled my steam overlay. I'm getting tired of the sudden mass of CTDs that started a few days ago.