Let me be clear about this: When you sight in from a hard surface, the rifle jumps and the resulting zero is actually higher than what the gun would be from a padded rest or sandbag. It's a false zero.

Did the boards/table contact create this situation even though a sandbag was on top of them? In other words, I need to know the boards introduced that same kind of jump effect? If they did, I need to resight.