Build 528 is the latest but it’s been out for almost a month now … I suspect the problem you are seeing is more likely a network stack environment issue than any change to Roon … but not knowing what version of Roon was running when it did work of cause means that can’t be conclusive.
If you still have the logs from that time … you might be able to identify the build number.
Let’s see if @support can shed any light … but iirc running Roon in docker is not officially supported.
Fingers crossed the root cause can be identified.