Damn, I just saw the #12178 and this is possible duplicate of it.. Though, I believe you can extract more information from my report, since there are logs attached, more detailed description, etc.
Same thing happens to me actually
Nothing extracted yet.
Your system information
Please describe your issue in as much detail as possible:
Expected: Games are downloaded as usual, without speed spikes.
Actual: When downloading any game (as you can see on the screenshot below, proton also counts), at the time progress nears the end (circa 90-95%, different for every download), the speed drops dramatically. This continues for few minutes (1-5) and then the game just finishes the download as usual.
Steps for reproducing this issue: