Checked Checkbox Not Stored

I think, I am doing something wrong, but when I check a checkbox in rendered mode and switch to edit mode, my checks are gone (- [ ] instead of - [x]). When I change modes again, the checks are still there. But when I change to another note and back, the checks are gone also. Somehow they don't seem to be stored.

I am somewhat irritared, because I think that I must have seen this earlier and it cannot be new as I have not changed anything to my Joplin config.

After some more playing around, it seems to be a behaviour, that is specific to this certain note!?

Even more strange: when I check any box in rendering mode, the first line of the note gets rewritten from - [ ] 12 Monkeys to [ [ ] 12 Monkeys.

Win7 desktop, Joplin 2.8.8

Can you export and upload the problematic note file?

Very odd...
May have something to do with Checkboxs appear but are nonfunctional if markdown is malformed · Issue #4070 · laurent22/joplin · GitHub ?