replace text issue

[thwaller]

I am using version 0.9.0 of Metamorphose 2 on Ubuntu 18.04.2. I am attempting to rename the cover art jpg file for a series of albums. I am using the replace function, what to replace "cover" and replace with "folder". This appears to be causing some sort of glitch as the preview gives a warning for all matches showing original name of "cover.jpg" and new name of ".jpg", basically removing the file name. If I use some other text in place of "folder", like "somename", it works just fine.