Screen shot please?

https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

After I paste say from a pdf then the problem starts and affects my new text entry.

Your imported text is probably bringing in with it some formatting that Thunderbird fails to interpret properly. Possibly to do with hanging paragraph indents, which are not likely to work reliably in HTML. HTML ignores white space, unless it's converted to an explicit spacing/positioning instruction, or replaced by <br> tags.

Try Edit|Paste without formatting (or ctrl+shift+v).

Or paste your cuttings to Notepad first to sanitize them.

What happens if you select the imported text and re-apply a Thunderbird style (e.g. "Body Text") to it?

Oh thanks it is fixed if I select the problem text, go to Format button and select "increase indent."

I can't easily see, "body style," but in looking I found "increase indent," thanks