Sounds like you have a project on your hands.
Yes, corner leaks can do a lot of damage when they get large enough. Water gets in, gravity takes over and the water heads down.
Often times when enough has leaked in, the walls get wet inside and it keeps flowing down. It becomes trapped above the plastic membrane on the bottom of the camper which is intended to keep road splash water out of the camper. Over time and enough water, the water flows left, right forward or backwards along the outside of the camper under the plastic membrane. The water then can start rotting out the band board around the campe, wall studs, floor joists and whatever is in it's path.
Good luck with your repair. If you need any help or tips, this is the place for Sunline info. Ask away. Many here have done all kinds of repairs and willing to share.
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
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