Sometimes this can happen with too much glue in the point, then not enough pressure during clamping. We're splitting hairs here though... The glue line should be non-existent for the most part, though there may be some slight visibility of the glue. Basically, if the glue is visible then you may very well end up with the ridge you describe.
The wood itself will shrink and expand with humidity/temp changes of course. The glue, on the other hand, changes differently. The glue, the finish, and humidity/temp are all related. Later, we sometimes get a surprise like you did.
Over the years I've figured out that a glue line is less visible if the two adjoining surfaces are not too smooth. You could rough the surfaces with 100 grit prior to gluing to "fluff" it up. Surface prep is huge.
-Doug