TodoList 6.4.8. invalid argument found

I have the following issue:

TODOLIST works fines until it comes to paste something into COMMENTS.
COMMENTS are set to RICHT TEXT.

E.g. you are copying text from a website - lets say an adress - to the COMMENT and you try to save the task, a window pops up saying INVALID ARGUMENT FOUND.

It does not matter if you paste the text directly or if you first paste it to an Editor and copy it from there to the COMMENTS. So I do not think it is a format issue.

I also tried to import the same text from a csv-files: Yes, you can import it, but once you try to copy it to a different location within the tasklist, same failure pops up.

You can not save the tasklist until the pasted text is removed.

Or: you remove all "blank lines" and all "returns", than tasklist can be saved.

This happens only if text is pasted from "outside" the program initially.

If you type the text in (within TODOLIST) - no matter if "blank lines" or "returns" - it can be copied to any tasklist you want.

Any idea how to solve this? Thanks.....