When I upload a file to https://cloud.privacyy.ch I've to set File chunking to 1.5MB I also had a problem with file downloading but that was redis. I disabled redis cache..
Still, if I want to upload any file without chunking it would've 10MB/s and then goes down immediately to some KB/s like 700 and then slowly to 100KB/s and then 10KB/s. At the end you just stop it.
During uploading there's a time when the server has 2 apache processes using 100% of one core. Also later on the apache processes have to wait more and only use 10% but the hdd is loading. There's no special change on upload speed - it just slows down and once the HDD goes well again the apache processes use 100% again. My cpu has 2GHZ and 2 cores (but is multithreaded).
An update of nextcloud didn't help
feel free to ask - I just don't know what logs I've to put in (there's nothing in apache error log)
ah, you can log in to the server by the user: test and the password: lester12345678 if you want to take a look at that special error
btw: max execution time isn't the problem, max post size isn't the problem and max upload size isn't the problem