Users get SyntaxError: JSON.parse while trying to enter a comment

Hi guys,

some users sent me the message, that my comment function (standard easy blog) isn't working. I tried by myself and got the message "SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data" (please see picture). However, i received already some comments. So I'm not sure if there are certain conditions causing the issue.

I tried it again and it was working...very puzzling. Maybe the issue is not always reproducable. However, as comments are the spice in a blog i would preffer that this function works 100%.

EDIT: Tried again and got error: SyntaxError: Unexpected token I in JSON at position 0

Thanks in advance
Marcel