Mahindra Max 22 HST clutch questions

[smack957]

I have a Mahindra Max 22 HST (not emax). I bought it used with 120 hours. I've put about 80 hours on it. I had not used the 540 pto until the other day. I borrowed a tiller. When I went to use it, it tilled fine at low RPM's, but when I put the RPM where it was supposed to be and hit some rock, the tiller stopped, but the engine speed didn't change. PTO shaft stopped turning. Once past the rock, it started spinning again. It did this twice. I am guessing the shear bolt in the shaft was too hard, since it didnt shear, but now I am worried about the clutch. Last summer I got into some tall grass with the 2000RPM belly mower and it bogged the motor down and killed it. So it was working fine. I have also not noticed any clutch issues with the hydrostatic transmission. My question is are there 3 separate clutches? One for tranny, one for 2000 RPM Belly PTO and one for the 540 PTO? Wondering if the previous owner sold it due to the 540 slipping and I had no idea since I had no 540 implements until now. I was thinking about getting a slip clutch for the tiller, but if there is a separate 540 pto clutch and it is slipping, I am not sure it is worth trying to till with it?