space acts like tab

When I enter a space between letters, several spaces are inserted. With “reveal formatting” set, only a single space mark is showing.
I haven’t encountered this before. I tried copying the line and pasting it into another text editor, then copying and pasting it back, but without effect.
Any ideas?

Probably paragraph with “justified” alignment. If you have a line break instead of a paragraph break, the “align last line left” setting may not take effect, which gives the behavior you describe.

Just keep on typing and see if it aligns nicely, or use left alignment and see whether that fixes it.

Thanks, but paragraph is left aligned. No special treatment of last line of paragraph. Problem persists.
Other ideas?

Sample file required. Edit your question. Use the paperclip tool to attach a file displaying the issue.

Software version and system type may be useful. Screenshot may also reveal some signs pointing to a cause.

What happened as you continued typing? Did previous words remain still? Did cursor jump to next line or continue past margin/paper edge?

I got it working, but can’t say I solved the problem. I just cut and pasted the line to another word processor (Roughdraft), then cut and pasted it back. Must be some kind of hidden non-printing character. But I had tried “Clear Direct Formatting” with no success.
Anyway, thanks for the help.