It occurs every time: Edit Package & body -> Ctrl + F -> Enter any text which you can find i this package -> Find next -> AV.
If you enter text which not occurs in package everything works fine.
This works fine for me. Does this happen for any source? I notice on your screenshot that the status line mentions "0 items found". Is that relevant? This indicates some prior action before the steps that cause the error.
I tested the following:
1. Start plyxon on Ubuntu 24.10
2. Open a package spec and body in a SQL Document
3. Type Ctrl-F
4. Enter "a" in the "Text to Find" field
5. Click on the "Find Next" button
Can you confirm that these exact steps cause the error for you?