I had a shield fall off earlier this summer. I did a ton of research and ended up choosing JB Weld epoxy. It was easy to apply and the shield is very secure now.
Before gluing the crest back on did you have to scrape/peel off the old glue?
One of mine just fell off. The old glue feels a little rubbery, like silicone but i can't peel it off my finger nail.