The next time your 235XLT doesn't appear to be receiving any talkgroups, come out of trunking mode and manually step through each of the programmed frequencies in your Charleston bank.
You should be able to hear the control data signal on one of the frequencies while stepping through the frequencies in manual mode.
If not, you're either too far from the trunked system sites, or you're missing one (or more) of the system frequencies. The 235 cannot do control-channel-only scanning, so you must have all the frequencies programmed to be able to follow all talkgroups.
If you had another trunked system previously programmed in the same bank, make sure the fleet map is set for E2.
Jeff Multer