solved, for "experts" its caused by bad timing belt damper.
I have the same exact problem on a totally different engine & car, just not as persistent, and so far was not able to pin down the issue. The auxiliary belt tensioner has been changed, have not gone as deep as the timing belt one yet...
The log discussion reminds of all the times at the dealership buying parts for my modded / engine swapped and turboed car, "Sir, we need your VIN number to be able to help you!" FFS.