@freemo I've had something similar before, but it's been a long time. I stopped using the federated tab on account of it being way too full of low quality content that made it hard to find anything useful + nsfw things I didn't want on my screen.
The federated tab is very much drinking from the firehouse in terms of content, and Mastodon has a default rate limit of three hundred API calls per five minutes (i.e. one per second, on a five minute average). I dunno if QOTO changed that - we have some things like post length limit that are better than default - but there's some limit, anyway. My working hypothesis is that just fetching the new posts gets pretty close to whatever the cutoff is, but doesn't bust it; and sometimes the web client has to make additional API calls that blow the budget. The quoted post mentions that a video came up, so fetching the media file is a plausible additional step that could be to blame.
I believe there is a "slow mode" in the settings. Maybe try that and see if the problem goes away?
@ClaraListensprechen4