Forms page cannot be loaded if WP Homepage is set to a static page

WordPress 5.6.1, ChronoForms7
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Clicking on Preview->Front (e.g. http://localhost/mysite/index.php?page=Chronoforms&chronoform=my-form says page not found. The form loads ok when embedded with a shortcode in a page, but again results in a page not found when submitting the form.
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After some trial&error with a clean WP 5.6.1 install it turns out that this problem can directly be reproduced by setting the default homepage of the WP site to some static site rather then default recent posts setting (in wp-admin/options-reading.php)
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Unfortunately, this is a showstopper for me, I can't change the homepage on a a production site just to work around this problem.

Actually, the workaround doesn't work completely. Although the form page loads, after I submit the form, it tries to load http://localhost/my-site/my-page/?chronoform=my-form&gpage=end_page - but can't find it.
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Again, this is with a WP 5.6.1 installed from scratch.