Same thing happened to us last summer. We had stopped at a Walmart to get some groceries for later and I noticed the skirt had popped out of the gasket on the driver's side slideout. DW and I popped it back in and I applied a bead of clear silicone over the joint and it has not been an issue since.
Mikendebbie Austin TX - Aggie '77
2019 Chevy 3500 High Country DRW
2018 Montana 3921FB
Three cute Aussies Gus+Fern+Jimmy