Kubota b21 front wheel drive issue

[Camcubota]

I have a kubota b21 that pops out of front wheel drive (4x4) when starting off. For a wile it would only happen when reversing. I should mention it’s a hydrostatic trans. Has anyone else experienced this problem. Or fixed it. Any info helps

 

[L35]

Is it manual linkage? I’d start by looking at all the joints for slop or damage.