When Gibbs first writes "WALK AWAY" on the white board, he writes it at an angle. He then walks around the room and tracks down the hidden bug. When the white board is seen again a moment later "WALK AWAY" is now written mostly level with slightly smaller letters.
Vance and Bishop are in the MTAC, talking remotely to Deputy Director Ellis. The folds in a flag behind her change between shots. In the first shot, the first 'A' in the motto 'Semper Paratus' is partly obscured (and looks like an 'E'). In subsequent shots, the lettering is clear.
Crochet is a continuous process, which cannot be interrupted to create letters. Cross-stitch and embroidery are how letters are usually added to textiles.