This post will seem totally out of context - oh, well -

I would free up the I-strut upper mount using an X-acto blade like pictured. You can use a tack hammer on it like a hammer-n-chisel. Light, light taps. Clean up the inside of the gap with the same tool. Clean up the sides of the upper mount with sand paper. Reglue and use spring clamps to keep it from creeping.

HTH