In the almost 30 years i am in boat business and miles and miles of caulking using Sika PU caulk or adhesive i never ever had it debonding, but had a lot of debonding using silicone stuff, both materials with throughly degreasing with thinner.
But you are right, i have debonding also in my house shower on marble, probably was too humid or bad degreased by the plumber.
From the feeling i guess ex owner used 4000 UV to caulk the seam between the rod holder board and the gunnel at least a year ago and it still looks nice and shiny and no debonding at all, but i am not sure what was used, it looks and feels as 4000 UV.
As Ky Grady wrote as well:
use a cutter or razor blade to cut thru the PU caulk and then shave it off with a razor blade, they can be bent to the right curve if necessary. leave either the remaining thin but clean film or use thinner to rub it off. Yes, it need a bit of elbow grease but i prefer that than a leaking seam.
Insted of a cutter PU caulk can be cut with a braid or monel steel wire, thats what body work shops use to cut car windscreens from the frame to replace them.
Chris