I find when dealing with a vexatious LGV it is best to sell it and buy a HW99S or an HW30S, which will reward thoughtful tinkering with superb performance.

Walts are supposed to be perfect out of the box so why fiddle with them? 40mm of pre-load sounds like a total armful of old washers, I'm surprised you could pick it up.

Seriously though, perhaps the TX spring is overspringing it with all that preload, try it without. Too much spring can result in lower fpe as well as higher fpe.