Massey Ferguson 500 Series Combine seeder Clutch problems help needed

[krankieone]

So after less than 1/2" of rain since Christmas we get an inch or more forecast for today so I disced up a paddock and got the seeder out yesterday greased it up filled it up with seed & DAP and then as soon as I get much over 1- 2 mph the clutch trips (I normally have to sow @ 7-8mph) tried disconnecting the small seed box same deal then the main seed box still tripping the clutch tried to free it up a bit more out it the paddock for a couple of hours by this time I'd run out of daylight so I dragged it back to the shed bucketed out a few hundred pounds of fertiliser. I pulled out all the stars and found a few down tubes blocked by spiders nests causing the fert to back up under the stars relubed everything and reassembled it all it turned over OK by hand as it was nearly midnight I packed it in for the night. This morning filled up the fert box back out to the paddock same thing disconnected the fert box now I could get about 5 mph before it tripped out.

I'm pretty stumped at this point but am suspecting the clutch is breaking out a lot earlier than it should If anyone has can offer any insights or suggestions it would be greatly appreciated