Hello,
I think it is better to check if you have some time slots faulty of that TRX. It is recommended to do a TS check using TEMS.
In case of TRX or TS faulty you might face a lot of TCH drops, in case the problem is with the SDCCH TRX then you might face SDCCH drops.
Try to identify the SDCCH TS on another TRXs as well.
Good Luck