first of all, it took me 5 hours to find out that the error was based on zhe update to 2.1.7. I really checked every logfile i could find on the server to see whats happening - nothing -
I saw the upload process with a grep on my local ip in the stderr but suddenly it just stopped, no error, no warnings.
But i do have some suggestions to make everybodys live easier:
1. Toggle debug mod should also show a state (0,1) to see if it is on or not
2. Place of core dumps should be changeble, our /tmp is only 1G and it run full twice.
3. If Admin email is set, put a checkbox there to define that core dumps are sent with mail, even if core dump is deactivated (override), the server died twice tonight and i dont have core dump because of /tmp might be running full again
I cpuld see in the core files, that there where errors complaining about HTTPS. It said that the page requested is only allowed in HTTPS, checked all vhosts and could not find any errors what this could cause.
I also can not update a produktion IP server to 2.1.7 because we get to many problems with our developer teams due to upload errors.
The test IP could be used, but the error seems to be harder on load. On the test IP where only me is on the server, we can reproduce the error but it is different behaviour. Sometimes the upload works, sometimes it doesnt, and if it fails i dont see anything in the DEBUG log.
So i suggest implement suggestion No 3 to make it easier to debug.