Jigoshop intercepts all comments posted and throws exception

I have been having a curious issue lately. Whenever a user posts a standard comment on a post on my site, they get a HTTP 500 error. I debugged it and it comes from Jigoshop eCommerce 2.1.10:

PHP Fatal error: Uncaught Jigoshop\Exception: Product review must have rating. in C:\inetpub\wwwroot\wordpress\wp-content\plugins\jigoshop-ecommerce\src\Jigoshop\Service\ProductService.php:434 Stack trace:
#0 C:\inetpub\wwwroot\wordpress\wp-includes\class-wp-hook.php(288): Jigoshop\Service\ProductService->saveReview(1, 0)
#1 C:\inetpub\wwwroot\wordpress\wp-includes\class-wp-hook.php(310): WP_Hook->apply_filters(false, Array)
#2 C:\inetpub\wwwroot\wordpress\wp-includes\plugin.php(453): WP_Hook->do_action(Array)
#3 C:\inetpub\wwwroot\wordpress\wp-includes\comment.php(2015): do_action(‘comment_post’, 1, 0, Array)
#4 C:\inetpub\wwwroot\wordpress\wp-includes\comment.php(3137): wp_new_comment(Array, true)
#5 C:\inetpub\wwwroot\wordpress\wp-comments-post.php(25): wp_handle_comment_submission(Array)
#6 {main} thrown in C:\inetpub\wwwroot\wordpress\wp-content\plugins\jigoshop-ecommerce\src\Jigoshop\Service\ProductService.php on line 434

Jigoshop seems to catch all comments and treat them as product reviews. It causes the exception.

I have this exact same behaviour on two hosts: Linux/Apache and my development Windows/IIS server. Disabling all other plugins doesn’t help. Changing the theme doesn’t help (I switched to twentyseventeen for a try).
One Jigoshop setup was migrated from the old Jigoshop plugin. The other was rebuilt from scratch after an upgrade failure and corruption (I had to purge jigoshop from the WordPress database by hand and install the new plugin). Yet they both behave the same.

I am a bit puzzled and it can’t stay like this. It would be nice if someone could advise.