Never heard of it but a little googling and it looks more common than I would have thought. maybe it goes un noticed for most because you can't see the Cap while driving.
There was a topic on here discussing it a few years ago:
Front cap "cave ins" | Good Sam Community - 3324177
and over on IRV2:
https://www.irv2.com/forums/f50/front-cap-caves-in-at-highway-speeds-on-keystone-cougar-tt-460407.html
General consensus is that it's the wind pushing against the thin fiberglass where there is a lack of structural support. Left unattended I imagine it would start to crack and really be an issue. Some mentioned trying expanding foam behind it.