The Amazon Echo Dot and Virgin superhub do not always get on together. My Hub2 seemed to cause the Dot to crash when connected to a bluetooth speaker.
Others on here have had the same issues. Some report it's ok with the Hub3.
My solution was to put the Hub2 into modem mode and use a router for wifi. Easy to do.
My wifi is now stronger and no issues so far with the Dot attached to a bluetooth speaker. It just plays as it should. Time will tell, but so far so good.
So if you are having issues it's worth a try.
It's amazing how many issues are fixed when using the SH's in Modem Mode
I've been using Modem Mode for years ............