This is the down side of sheet. It looks nice, but repairing is very dificult and seam seperation is one of the biggest downers.
What you need to do is to carefully open up the seam and remove any dirt, grime, or foreign particles.
Then get some good seam glue or mastic that is water proof.
apply the glue with an artist brush or popsicle stick to get it far back under the vinyl seam.
Now with your hair dryer, carefully apply gentle heat to the seam this is to make it more limber and pliable. Press the seam down to the glue and wipe away all, all glue reside.
Lay some wax paper all along the seam and place a book or bricks or any heavy weight all along the seam. Keep on for a day or two.
This should do it.
Then, get some seam sealer and go all along the seam and apply this. This will weld the seam together and not allow grim, water or whatever to get there again.
fly your flag.
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