I noticed that redirection to a menu item stopped working in v J3.7.4 and seblod v 3.12.2 and it seems to stop the email too... (but not quite sure on that)
Where did you set this redirect?
I can't get your image attachment method to work, so here it is in the Config area of the Form/Content:
https://coldwork.com/images/screenshots/redirection.png
Content is redirection to a content view of the current item, not menu item.Menu item setting is a setting that tells redirect which Itemid to use on this redirect.
And both stopped working after an upgrade... Only my config message appears, NOT the content view and while the menu itemID appears to show state (ie hightlighted), it's clearly the home page content below the config msg.
I just tried and it works correctly for me with seblod 3.12.2.