Welcome to the Forum.
I would first say reset the MZD Connect system (info on how is on this forum somewhere, I know for my car, the button combination was different from the USA derivitive).
Failing which, it may be faulty buttons or most likely the connection of the controls to the MZD connect system.
Are you sure that you system hasn't been modified before and just not put back properly?
Check you firmware details etc. I've seen multiple 'guides' where people remove all the MZD connect parts to modify/hack them.
It may just be worth while going to a dealer to have them test and tell you, may involve a cost.
Hope it helps.
2016 Cx-3, 2.0L petrol, manual transmission. South Africa.