I had a camshaft (rhs) seize last month and am just putting the new parts back in. The front two bearings seized on mine due to the shifting of the oil supply pipe so that the holes in it didn't line up with the plastic tees anymore. It's my understanding that the oil feeds from back to front as the rearmost camshaft bearing has a groove around it's circumference to allow oil from the block through the bearing and into the oil supply pipe. The other bearings are smooth.
I still don't know what caused the oil supply pipe to shift position. I plan to lock it somehow so that this won't happen again. IMHO, the cam oiler design could have been better executed by MB and owners should replace the pipes and tees annually seeing how their failure causes $$$$ damage.
Even a broken clock is right twice a day.
'66 MGB Roadster
'85 Mazda RX7
'91 Chevy P/U