Makerbot Replicator 5th Generation Problems....

[Mjolinor]

You are not thinking about it.

If you adjust all three then the plate moves up and down
If you adjust front left then the table rocks about a line, back middle / front right
If you adjust front right then it rocks along the line front left and back middle
If you adjust back middle then it rocks about a line front left / front right

That is the only way to ensure that the table is flat and at the correct height. Four does not cut it at all.

If you have four screws then one of them is either doing nothing or it is bending your table.