Sami- Aye, the building discrepancy was cleared up for me. I'd suggest to new players that, in building a wall, one should face the character directly where they intend to build the wall and take one step backwards. That is, in order to build an east wall, move north, bump into the north corner and take a step backwards. That should avoid the optical illusion that led me to my error.
As to the arrow bug, I've wondered if it had to do with me playing for 18 hours without restarting my comp? I can't duplicate it, so, I guess I just messed up. Sorry!