ERROR: [Script Filter] JSON error

[WWG1121]

execute 'wf.send_feedback()' occur error:

ERROR: [Script Filter] JSON error: JSON text did not start with array or object and option to allow fragments not set. in JSON:
not support XML format?

[Tanky-Zhang]

how can slove? I also encountered
@deanishe hi bro， coud you help me

[roeniss]

In my case, some debug-purpose print makes JSON confused I guess. After changing all print with log.debug (as official doc guide), the problem is gone. I hope this helps you guys.