scalloped edges on square and rectangular prints

I currently run 4 Flashforge Creator printers. Two are of the older wood case variety and two are the newer metal case types. The two older ones are developing problems with scalloped edges when printing square or rectangular objects. Multiple attempts at leveling do nothing. It's typically on one edge (and the same edge) of the print, but it can at times show up on a different edge or sometimes even on opposite edges of the same print. The scalloping is typically only on the first few layers as well. The upper layers are fine. Since this isn't a problem (so far) on the metal cased printers, I'm assuming I'm dealing with some loose bolts somewhere. Anywhere in particular I should look?