This is one of the easiest, if not the easiest, thing to spot and correct – not pointing it out is just straight up laziness. You’ll notice this affecting your set the most on days when it’s windy or there are particularly strong gusts due to the wind catching the blades at different times (vs. at relatively the same time when squared together). Make sure you and the crew know where they should be squaring the blade and make the call if you see someone squaring (and likely entering the water) late. For example, we square over the toes, meaning when the handle is over the toes, that’s when the rowers square the blade. Other common spots are half-slide or at the ankles.
Bodies not moving in sync
It’s not just about getting the blade in the water at the same time, it’s about syncing up (in this order) the tap down, the hands away speed, the rocking over of the shoulders, the timing of when the wheels start, the point at which the bodies should be set, the unweighting of the hands to drop the blade in, and finally the timing and smoothness of the leg drive. Making the call to get the catches in together is fine if you’re coxing novices but if you’re in a boat with anyone more experienced than that, your (and their) visual cues should be focused on matching up the body movements. You don’t need to see the bodies to do this either – just make the call and confirm via video review later who the specific culprits are so you can make more targeted calls the next time you’re out.
Lack of rhythm or pace
If the stroke’s pace or rhythm is inconsistent or you’ve got rowers rushing the slides into the catch, the boat’s going to be off keel more often than not. A lack of or inconsistency in the pacing will make it tough to follow and if the rowers can’t anticipate what the stroke is doing, they’re not going to be able to match up the body movements that I mentioned in the previous point. Alternatively, if rowers are rushing into the catch then as they rotate out towards their rigger their weight is going to get thrown down to that side which in turn will pull the boat over (and result in a lot of smashed knuckles against the gunnel as that side tries to take the catch).