Thanks for the response ZeroByte.
Your suggestions make sense. I have been trying to learn about trees and mangling, and thinking of trying a stripped back version of what alaskanjackal posted here:
https://forum.mikrotik.com/viewtopic.php?f=13&t=73214&start=50#p589727
For now using anything other than pcq-upload-default on the upload queue works fine. I’ve found a few other forums mentioning this issue, it seems specifically to be a problem with high asymmetric lines and pcq-upload and there doesn’t seem to be a solution besides changing the queue type, setting pcq-rate or possibly tinkering with burst:
http://forum.mikrotik.com/t/strange-pcq-issue/97029/1
http://forum.mikrotik.com/t/8-mb-line/98290/6
All of that is fine, and maybe they are best practice I don’t know, but for beginners like myself this is a stumbling block and time sink, since something seems broken. Why do the other queue types work and not pcq-upload-default in this scenario. Is there something we are misunderstanding? Is pcq-upload something that shouldn’t be used on asymmetric lines, or low Mbit bandwidth lines?
To reiterate, as mentioned in other forum posts, no matter how high or low you set the upload max-limit on the simple queue compared to line-rate – eg. you could have line rate up 1500k, simple queue upload max-limit 200k – this issue will occur, and download seems to almost get shaped down to the upload limit.
Thanks for your help.