Editing in Studio 2 plugin adds unwanted transparency in PS

So the topaz studio 2 photoshop plugin for some reason adds some transparency (or at least the checkerboard pattern) to the edited layer after coming back to PS. It’s happening even if I make no changes to the image and only click “accept”. Opacity is always at 100%. What is the reason for this?

PS. Flattening the image in PS seems to be the only way to get rid of it, but I don’t want to flatten all my layers nor do I want to create a new document to flatten just the layer edited in the studio and copy it back to the main project.
PS2. TS2 doesn’t add transparency only when I edit in a project with 1 solo layer.