i wase not here, but i can explain why i call this problem SDCCH CONG.
if you have RXLEVACCESSMIN=-110dBm and some MS trying to acceed to the network with level between -100 and -110, BSC allowe an SDCCH during (T3101) and the link is lost. many cases like this can block 8 sdcch if you have 1 trx or 2 TRX in one site whithout neighboor.(i use this cell in SAHARA for some offices)
so RXLEV ACCESS MIN wase the solution to reject MS whith bad signal. I can use RACH TA FILTER but i prefer this solution. Excuse my english i speak only in french.