Need Help! 1996 John Deere 8875 boom and bucket shuttering when hot

hi guys I need opinions... I have a John Deere 8875the model is from 1996 the motor runs strong and the machine is still tight has way too many hours for the meter to read and a horrible repaint on it. the machine runs my badco excavator attachment without a problem on auxiliary controls. everything worked wonderfully until 3 days ago. The machine runs strong for about 10 minutes until it warms up then I lose proper controls of the boom and buckwt..they start to hestitate at first then shutter an inch at a time under load.they won't left off won't back down won't do anything properly then when I take the weight off them they move slowly back to the regular seated position. When the unit cools it works well again. It is not overheating and all filters and fluid s were changed. I called the Deere shop and a service rep said by the symptoms it maybe a solenoid (part mg86507510) or solenoid support ( part mg 86507506) but he said no promises. He spoke on the phone that I had to lift the cab to change these out and gave me instructions over the phone how to do it which didn't make sense to my setup so I started to question his judgement. Does anyone have input with more certainty?

It would be greatly appreciated. I would hate to buy these parts and install them to find out it doesn't help.

Thanks for any input you guys have.

Need Help! 1996 John Deere 8875 boom and bucket shuttering when hot