typical problem due to large coverage : MS with a very poor rxlev will face failure during paging response or channel request.
other possibilities :
check frequency interference and uniqueness of BCCH/BSIC in the area. Check also the occurence of TCH/BSIC if TCH of neighbor cells can use the same frequency as the BCCH of the problematic cell.
check also the path balance of this cell.
finally, check this cell’s coverage : are there resurgences that would force this cell to carry far-away traffic, with low rxlev ?