Sealing Trunk Lid Rubber Seal

[Tumbleweed_2]

The rubber seal that grips over a metal lip (going around the opening for the trunk) works loose after 18-24 months, resulting in water entering the trunk and causing the tops of things sitting in the trunk to become wet. I have isolated this issue to the rubber seal because I can remove the seal and using a pair of pliers tighten up the 'clenching' strip inside the seal, reinstall the seal and verify there are no more water leaks.

Is there a waterproof, preferably non-hardening(?), sealer or caulk I can apply inside the clenching channel of the rubber seal (before reinstalling the rubber seal) to created a long-term solution ? Thank you for your feedback.