The problem stems from the fact that the pressure plate is a pressing .
This pressing is done to a blank cut or stamped out of a sheet of steel that was delivered as a roll so it will want to curl.
the blanks got tossed into a stillage then lifted out and put into the press so the spring holes have a random orientation with respect to the grin of the steel.
As such, some plates will always bend while othere will almost never flex in use.
This explains why some go mad and still never get a clean lift while others will get a pefect lift with no problems at all.
The next problem is the lift itself.
You have a flat end of the push rod pushing on a point with nothing to support it or hold it strait.
Thus the use of the top hat push rod where the pushing surface is a flange, held perpendicular by a length of rod inside the mainshaft.
Simply fitting the radial roller bearing and top hat lifter, available from SRM will make a world of difference.