*Have checked
all rails and stiles for squareness of cuts, groove for correct depth
and that the panel grooves line up. *

Check that the style/rail grooves are cut straight, all along their
run, no slight curves WITHIN those channels. Also, check that the
panel edges are cut straight all along their run.

The channel ends may line up, but there may be a "bend" (curved cut,
somehow) in a center area, somewhere. Same with the style/rail
channels.... the ends may align, but an edge may have a curved cut
(somehow), somewhere. The boards may be flat... it may be a cut that
is not straight.

Flip the panel over, right-left & up-down, install each application.
Does the problem still exist in each application?

Sonny