i can see a good effect on SD Drop, but that may be due to the thing you did to fix the transmission problem. You may have reset the BSC, which may enhance the processing of the SDCCH signalling ?
The enhancement on SDCCH estab succ % is much subtler. Maybe you ought to wait a longer period for this one.
Anyway, back to the SD Drop.
During the SDCCH phase, depending on your vendor, the UL PC may kick in especially if the SD phase is long (especially during SMS transmission, which uses SDCCH for a longer time). Indeed, the PC might be deactivated for few seconds, (ALU default : 3 sec.) and then will be started, even if you are still on SDCCH phase.
Which vendor are you using ?
On BCCH TRX, there is no reason (that i know of) that the vendor desides to deactivate the UL PC automatically. If you can share some documents about this, that’d be interesting.