bolt form success fails

I have bolt form with post processing on BoltFormsEvents::SUBMISSION_POST_PROCESSOR.
Forms show correctly, its correctly validated, if not valid correct messages show but if form is valid it fails just after mine post processing.
I've tried with feedback.success and feedback.redirect both fails the same way:
> Uncaught Exception: Twig_Error_Runtime .
>
> Twig_Error_Runtime in Template.php line 447:
> An exception has been thrown during the rendering of a template ("Attempted to access invalid result: boltforms.submission_post_processor") in "main-pages/join_page_form.twig" at line 6.

join_page_form.twig:
```

boltforms.bolt.yml:
```
join:
notification:
enabled: false
feedback:
success: Thank you!
error: There are errors in the form, please fix before trying to resubmit
redirect:
target: page/thank-you
templates:
form: boltforms\join_form.twig
fields:
...
```
It doesn't seem that boltforms/src/Submission/Result.php work with SUBMISSION_POST_PROCESSOR.
Please advice if its my error in config or issue with bolt forms and how to deal with it.

Versions:
bolt/bolt: v3.3.6
bolt/boltforms: v4.1.13