respond test with the firefox and chromium versions I mentioned :
In the first click to respond button, sometimes nothing happens

then in the second click the text box comes and when you send the message a page with {"id":5190,"parent_id":5188} comes only. But message is posted always.
I will try to cath the error in the browser console and write you.

The detail of the error you are giving is for this bug https://una.io/page/view-discussion?id=1081

Are you sure it does not only appear if you respond via a notification?

Hey Baloo, yes I've received same error message and it was also mentioned I think over in Online.me. I did click on ur link and thanks for bring this issue up as well.