@rfc2822 No, I can’t browse to the server from any device connected via Internet. On my local LAN the web pages serve up fine , and my Thunderbird calendar on a machine on the LAN will sync to the calendar on the Pi. However, I can ping the server successfully from the internet - both via direct IP address and the sub-domain name.
I do have a local DNS server running on another RPi on my LAN - Pi-Hole - to block ads. The Pi-hole logs don’t indicate that traffic to the sub-domain are blocked. But the DNS blocking would be happening from DNS resolution requests from devices that are connected on the LAN, not traffic coming into the LAN.
Yes, we know of this. It is caused by another library we use and which already had a fix for it, but in it’s current master the bug appeared again (and we used the master for the latest DAVdroid). You need to wait until we release 0.8.4 or (as you said downgrade temporarily).
Keep in mind that only the display is wrong - the bug appears based on the day where we are right now. This probably won’t show wrong again tomorrow or in some more days.