I should have mentioned that although the setting says 1/4" for the name the bit is actually 1/8" (3.18mm). The bit has a 20mm flute and the total cut depth I’ve been using is 19mm which gets it just through the 3/4" plywood. It is 90deg to the spoil board (1/4" MDF). It gets about 10mm into the board before it goes nuts…
So I went and removed the router and the mount. I found the mount part on the Z axis a tiny bit loose so I tightened the crap out of it. Then I reattached the router mount and put a layer of duct tape where it grabs the router. Reattached everything and tightened the crap out of it. It does not move at all now. I will have to wait until the weekend to get out there in the morning and try again but I have a good feeling about it. I’m thinking maybe it vibrated just very slightly loose or the PLA is somehow softening sitting in a 105 deg. garage day after day. Its PLA+ which is more like ABS than PLA so thats weird…
Hopefully have something to mount my laser to by then as well.