There is nothing wrong with any switches, so don't waste time and money with them. To help make sure that you know what is meant by ground issue, the problem is poor contact with the metal tabs on the tailight sockets and the housing.

Also over 90% of the fgf around have crossed wires on the tailights, the reason for all the cookie monster eyeball display. One wire powers the tail brake function, the other one powers the brakes, or whatever combination.

The point is that there are 3 light functions from 2 sets of filimemts and 2 wires, all of which are grounded through the metal tabs on the sockets. All of this has to be in proper working order.