Failed to decode JSON: invalid character '<' looking for beginning of value

Hello Folks,

I'm having an issue with the Kapacitor. The message **_Failed to decode JSON: invalid character '<' looking for beginning of value_** when i'm trying to Save the Alert rule. Any idea or same issue that fix this?

No source file, test, or entry point is named. Reproduce saving an alert rule in Kapacitor and capture the response that produces the JSON decoding error; done means identifying why the response begins with '<' and confirming that saving the rule succeeds without the error.

Written by the indexing model from the issue text.