@devkid DAVdroid 0.8 didn’t use okhttp, thus it didn’t support HTTP/2 / SPDY.
Now it does, but it doesn’t work with your server. How can you know that DAVdroid is the problem? I have heard this argument (“everything worked before”) about 10.000 times, and in 9.999 times the problem was not DAVdroid.
I’m interested in getting these things working and I don’t know whats the cause of your problem, but “it worked before, now it doesn’t, so there’s a DAVdroid bug, fix it” is not an accurate bug report and it won’t help getting these things working.