Testing the switch would be the first step(if those switches get a ton of use, they can wear out). Personally, I got sick of reaching for a talkback switch and sick of "producers" that would always start talking before I reached it(or would forget to push the button I gave them), so I automated the whole process. SoundRadix has a free plugin called Mute-o-Matic. Put the plugin on an AUX track, set the AUX track input to one of your preamp outputs and plug in any mic that can sit nearby. When you roll transport(to play or record), the plugin mutes the mic. When you stop, the mic is on for talkback.
I actually ran 4 instances with mics in CR(boundary mic on the desktop), drum room(boundary mic on the ceiling), Main room(boundary mic on the wall) and producer's desk(boundary mic on that desktop). Its also easy to insert compressors to control levels, or EQ to increase intelligibility. I know some that will cringe at the idea of talkback being open(non-switched), but everyone got so used to it that it was never an issue here
