blaze spawner looks like 2 blocks came off their sticky piston face and left hanging over the pressure plate. i stood back and watch and they wouldn't walk off that block if they spawn on it for some reason.

also i watch 2 blaze stand on top of the spawner and not move off for over 5 min, might want to put some blocks over that

Sometimes Blazes get stuck behind the pistions, and that prevents the blocks being pulled back. It's just a natural thing that happens to these types of farms. I will have a look next time I am there.

You'll have to speak to Nath about putting blocks on top of the spawners though, as he built it. I know it was hard work though, so I doubt he'll want to change anything! I've never had a problem with the spawn rate anyway. I just akf for 20 mins and get over 40 levels and stacks of Blaze rods using the splash potion/Looting sword trick...

So is it normal? Or is there a need for a check?

I think every now and again it's good to go in and 'reset' the pistons that have become stuck.

I will tell Nathan then