Afterwards, all subscriptions for GitHub commits, Reddit topics (and several misc forum topics) were marked completely unread (about 2700 articles…).
Debugging the feeds never has presented any issues.
For some of those blogs, the article time is reset to the exact time tt-rss fetched the feed and marked all articles unread, not the actual time). This is not the case for all GitHub and Reddit subscriptions right now (which previously didn’t exhibit this behavior anyway, so I’m guessing this is only due to some change between the commits I linked above).
In that sense, it’s very well possible I’m describing two separate issues here, which have the same outcome.
I have had several occasions where some subscriptions were “reset” in terms of read articles, but never on this scale. This was, however limited to some blogs I run. The RSS
lastBuildDates were never changed by the blog itself, so it was definitely something in tt-rss on those cases, too.
I’m running tt-rss on PHP 7.3.6 and MariaDB, provided by a hosting company. There were no event log entries. If I can give more specific info I’m not aware of, please let me know.