Hi. Found this exactly same problem when set "map factor" bar setting left.
In vehicle you open and close map many times, all 3D sounds get silence and not reset back.
After this problem, if you set "map factor" bar right, 3D sounds volume work opposite when open and close map.

This bug still exist.
I found one explanation for this problem, it maybe have to do with group and group leader "command" ?? Not 100% sure.

*update
This seems happen on every air vehicle. (While you are in air ?)

I have found this exactly same issue.