Hi! I've run into the same kind of problem; it's only on the itch.io website, not your github link or on the downloaded itch.io app, so there's a large chance it's not relevant.
It's not just the frame; the text boxes themselves seem to be cutting off. 
Here's the github/permalink version: https://watabou.github.io/perilous-shores/?seed=1114274662&tags=archipelago,wetl...
Obviously not a huge deal, but just wanted to file a bug report / let you know it's something that happens occasionally