I have a favorites list for the county TRS and a separate favorites list for all the various conventional frequencies in the county (local FD/PD/PW frequencies).
Trying to hear the county TRS is a miserable experience on the 436 or any other scanner. Reception is very sketchy in some areas because of the known issues that scanners have with the simulcast distortion on P25 simulcast systems.
I don't really know what the issue would be if you have simply imported the West Chester conventional channels. If you haven't changed any settings, what is imported should work.
Some BCD436 units have a known issue with internal interference from the circuit board causing reduced reception on the UHF band. I know mine has this problem. It is not an issue when I have an external mobile antenna attached to the scanner, but reception does drop off when using a rubber duck antenna. I have noticed issues in the 450MHz range on mine...bad enough that a UHF repeater a few miles from me is barely readable on this scanner when it will be full quieting on any other scanner or two-way I have. Perhaps you have this issue, too...only more pronounced? The spurious signal on UHF is not a myth. I can set a commercial two way radio near my 436 and have the signal strength bar light up more and more the closer I slide it to the scanner. For a flagship unit, there is a lot I find frustrating or disappointing with the BCD436. I only continue to suffer with it because I got mine at a discount and like the on board database since I travel around a lot.