MS To Do: Always Maximum Volume

The volume for Microsoft To Do regularly resets to the maximum level, despite a daily ritual of setting it to around 25% every morning.  This is annoying, as I usually start up my home office earlier than the rest of the household.

Typical day: Open To Do;  Check off the first item; Completion bell rings throughout the house; Open the toolbar volume control; Open volume mixer; Reduce the volume of To Do. 

Next day: repeat.

All other apps maintain their volume settings.