This is a known issue that sometimes happens, but we haven’t been able to reliably reproduce it yet. However, I’d strongly advise try upgrading your Syncthing installation Debian first, as no-one here is likely going to be willing to debug the old v1.19.x release…
Thanks for the reply. I did update right after posting, when I did realize how old that was. I’m now on v1.29.6 “Gold Grasshopper” but nothing changed.