cam followers split?

[John Gould]

Hello, with the engine in the chassis I find that two cam followers 'stick' when the tappet screws are locked home, I expect they are cracked or split at the top. Is this a common problem or have I just been heavy handed? 
Does anyone know if it's possible to remove them by carefully lifting the block sufficiently (with all pistons level) - I find that there isn't room to remove them from above.
Many thanks, 
John.