So, I've not addressed this with the LBS as of yet, I will very soon, however, as having been faced with an identical issue (of the nature of those "push" buttons), this YouTube video shows a similar 'fix' for a button/switch (similar to the handlebar switch having the issue).
To jump around and get the overall point, look at 15 sec.<---->34 sec., then 2:27 to see the contact cleaner used, then 2:50<--->2:60 to see the application then to 4:07<--->4:13 to see the fixed end result.
So I guess the question is, how does one "open" the handlebar switch to spray the contact cleaner on the micro-switch?
I know, I know, let the LBS fix it, but I'll bet $20 that the part is most likely part of the Mastermind control package and it most likely won't be able to be obtained (just like the SRAM fork that the LBS says they have yet to get a replacement) [and they took a fork from another stock bike to resolve the 5-1/2 month wait....a whole other post].
Regardless of opinion, you can't damage anything with contact cleaner on a switch, and if it fixes it (like it did for my car battery tender), then all that remains is to figure out how to get at the innards.