Shelley, it's called seam tape and it appears what you are experiencing is fairly common. Some owners have carefully pulled the tape off, put it in a pan of hot water and reapplied (with caulk) by stretching it carefully. A Trillium
owner should probably give you step-by-step instructions.
Others, have removed the seam tape completely and filled the gap with caulk. Using a damp, scrunched up paper towel you could then apply "texture." Others just smoothed the caulk completely.
I like this treatment, after caulking the seams, hide them with paint! FINALLY... I made peace with my seams!
Here's some more links: help with seams