one key question is if you have problems with the router pushing away from the
workpiece as you lower the Z axis into the work.
a good benchmark for testing in the corners is to do a L (in the bottom left),
do you trace the same path going down, right as you do going left, up?
Left, then up is a particularly problematic action and may round the corner as
there isn’t lots of force to move the sled left, so it’s got a good chance of
sticking until the left chain starts pulling up, at which point it will swing
left, but as it’s being pulled up, it will round the corner
Down, then right could end up with a squiggly vertical if the sled is not
sliding smoothly don the workpiece.
you cn shift the workpiece over, and do it again at a different angle (and with
different amounts of weight on the sled)
does going closer to vertical help the L to be sharp?
when it’s sharp, can you reduce the weight on the sled and have it remain sharp?
is there any tendency for the sled to push away from the workpiece as the bit is
drilling into the workpiece? (do a reasonably deep pass so you can see this
if you can get a video of each test, that can tell us a lot as well.