Unless the moaning is lack of lubrication on your new piston seal or outside the compression tube I haven't a clue. When my TX 200 experienced cocking difficulties and the safety not resetting it turned out my cocking shoe was cracked and coming apart. A new cocking she solved that one. The cocking shoe on this gun appears to be pressed from some sintered material and sometimes breaks. This is especially true of the higher powered American versions of this gun but not so common with the ones at UK power levels.
Overly dry / AND / OR too tight of fit on the piston seal ..... AKA: honking