squeeze the suction hose... and look for cracks.
The paint can hide the crack, IIRC, there is a coil wire inside. To be honest, if this is not affecting steering (herky jerky) I don't think it's the return hose.
"...3. Had new hoses made for hooking up the diverter and new hoses to run to a new grapple
4. Plumbing was checked and rechecked...." When you get some light on the subject, can you take photos of the plumbing? What goes where?
"...when moving the joystick all the way to the right, when dumping, it made a sound like the relief valve was opening and the tractor's rpms slowed..." First part, sounds like it should but the tractor's rpm's should have not have changed even a little bit...
Shouldn't the 12v valves be open on one and closed on the other? You have the 2 hoses with the largest loop in picture 1, one hoses going to one valve and the other going to the other, Is that Right, that would also make the other 2 wrong. If the boom is working everthing before it is good, it has to be from loader valve on. It just doesn't look plumbed to me.
Yeah, hard to see the routing on the hoses, but it looks like to me that you have outlets B1 and B2 paired up, and it should be A1-B1 and A2-B2 as the pairs. But it's hard to see for sure.

I can tell which ports are labelled since I am looking at the new KBOH diverter on my desk (preparing for an install on a Kubota L3240), so I am interested in how this turns out![]()
I wonder if one of the spools in the DValve or one of the QD's is fouled with some debris, sometimes even new hoses are filled with crap from when they cut them with an abrasive saw.... Everything had worked as it should for over an hour before I started having trouble but I'll double check the connections...
I blew the picture up, and here what I saw, looks correct to me: