Thanks for the feedback 
Good to know it runs on a Synology 
There is a known occasional UI controller crash that I have had happen when saving settings. I am still no closer to isolating a specific cause however. A crash when changing volume controls however is new - thanks for raising that.
Have you had other volume control extensions active in the past? I shouldn’t matter, but it may be related.
Due to the amount of device churn I go through when developing and testing I must admit, I have got into the habit of resetting device settings via the ‘Load Defaults’ button and have not had any setup related issues for a while as a result.