I am getting rarely “Connection failure” and only when talking to Riftsone inside the Rift.
I found a solution to my "Connection Failure" errors and it's been solved for good... I never have any issues with anything anymore, it all just works
Basically you have to run your save file through this command line tool and it resets the online pawn stuff which fixes the Connection Failure errors for good
A good guide I read is here: https://steamcommunity.com/app/367500/discussions/6/1694914736016765979
/ ... there's a link to the tool you need in that link above to download the DDsavetool file.
General steps for GOG:
1. Copy the DDsavetool.exe to the same location your save is... for GOG it's in:
(So you'll then have two files in that folder: DDDA.sav and DDsavetool.exe)
2. Open a command prompt (doesn't need Admin privileges) and navigate to the above directory
3. Run the command: DDsavetool.exe -reset DDDA.sav
And that's it... it leaves everything else in the save file alone except for resetting the online pawn stuff which is what gives you the "Connection Failure" errors
Do yourself a favor and backup your existing save before you mess with it, but I've found the tool 100% reliable... I originally used it to get my PS3 save of 45 hours onto PC using that tool
There's other neat things you can do with the tool... the -u command will unpack your file to a human readable XML file so you can actually see all the stats, checkpoints, all that... you can even tweak some of those and use the -r command to repack the file back to the .sav format
Give that -reset feature a try on a copy of your save and see if it helps with your Connection Failure warnings