Is this when Folding or when adjusting the actual Mirror Glass ? if it is when they are folding or Unfolding into the working position, then it is possible that there is dirt on the contacts inside the switch.
I did a little “How to” on replacing the bulb in the switch ( Electric Mirror Switch Bulb Replacement (My How To)
I you look at one of the photo’s in that which shows the PCB
If you remove the Grey rubber pad you will find contacts on the back and also reveal the contacts on the PCB, if you clean both surfaces gently with something like makeup remover on a cotton bud it may solve the problem, my mirrors did not fold on command and it was difficult to Adjust the mirror glass both issues were solved by cleaning the contacts.
If you look at my “How to” its shows how to disassemble the switch
Hope this helps