This started happening sometime this past week. I've tested with a large file and a small text string. Encrypting still works, but when decrypting a small floating box appears saying error reading input file.

I'd suspect Python 2 being removed as a cause but I'm having the same issue on OSX Mojave. In Monterey 12.3.1, it's broken in Textmate versions going back to 2.0.19, at which point the Encrypt/Decrypt dialog box itself breaks.

Update: Recovered the data using Terminal. Still not sure what's happening in Textmate.