I have the same year camper. Mine is a 19 lite conversion. It's only been out in the weather for the last four years. Before that it was garage stored. Has the same front framing. I started pulling mine apart a month ago.
Not happy with Dutchman quality or structural standards. Sub par at best. The roof construction quality at the rubber roof to metal wall compression bar are the cause of ponding water at the corners since the day it was built. It's always been a concern but I never knew how bad it was. I found missing mastic, screws without sealant, a bend kink in the compression bar, and a general jackleg approach to roof weathertightness.
All hidden underneath that wonderful self leveling garbage sealant. A roof is like a car engine. It takes two surfaces with gasket and a mechanical attachment to seal it. Do you pour goo all over your engine seals??
All the miracle caulks and all the band aid fixes in the world are not going to help. You have a roof problem not a wall problem. The wall corner damage is the water trying to get out and it's taking the point of least resistance. If you caulk that corner you're making it worse. You'll trap and drive the water deeper and father down the sidewalls.
Your framing is rotting. You have no studs for the corner trim screws to hold into. You no longer have lateral stability in the front wall, and if like mine, all the cheap iron anchor bolts to the trailer frame are rusted through. If you want to see how much that wall is moving take it to a parking lot speed bump and watch the wall while someone drives over it at an angle. Keep an eye on the corner trim. The only thing holding it on is caulk. New caulk will rip off in less than a year.
If you want to know how bad your wood is ... take an ice pick an push it into the corner in a few places. Do the same underneath at the sidewalls starting at the front and going back to the first outrigger. You can also peel up the vinyl floor in the front exterior storage area on the left side corner to see the wall sill damage.
If you are intent on a caulk fix ... strip the sealant on the roof down to the top of the aluminum corner and compression bar joint area and reseal back to the bend down the wall. If you find any good wood a couple new screws will help. Leave the corners open and in the sun for a few days to dry out before trying to close them up.
I'm using Dicor tape to seal my corners after the rebuild. It sticks real well to the metal and it will still let the corner drain at the bottom if your problem continues.
The good part of the rebuild is getting more usable space. I'm removing that diagonal lower wall that wastes storage space and building an 18"x18"x48" pull out drawer on both side. Gave me a good place for my battery/solar electronics and an outside grill kitchen on the other side. By changing to lithium batteries and using PVC skin I've only added 55# to the tongue weight.