4200 John deere rockershaft control valve

[KYBuck]

The rockershaft lift will not come up unless I move the lever all the way into the up position. and if I leave the lever in the full up position you can hear it laboring and I cannot adjust the height.
The John Deeere dealer says the Rockershaft valve is bad. He suggested I check the screen in the hydraulic system and see if it is dirty, I changed the filters. Did not help. The new valve is $500.00, however, I found one on the web for 250,
Does anyone have any suggestions as to whether something besides the valve could be causing this. Is it safe to buy cheap parts.
Thank You:

 

[Tx Jim]

When 3 pt is raised will it stay raised? Have you checked for correct control linkage attachment of lever & feedback rod?

 

[KYBuck]

Yes it will hold a bush hog up fro several days. I have checked all the other suggestions also.
Thank you for responding. I hope to find a fix that does not cost so much.