"Could not parse time from lastsync" - asking for help

I run the mirrors at https://archlinux.org/mirrors/kescher.at/ and unfortunately, I keep seeing a rather rare "Could not parse time from lastsync" on the Arch mirror status site, curiously on both rsync and https. This prevents completion from reaching 100%, which is rather annoying to me, and presumably some folks that depend on the mirror's existence. I have my own monitoring set up to check lastsync, and I have no recorded failure. Same goes for error logs I have set up specifically to debug this. Does anyone here have experience in debugging this? I have no idea what could be causing this anymore.