Field validation doesn't work correctly after adding second form.

Steps:
1. Create new LP.
2. Add form.
3. Add e.g. date field and choose format.
4. Submit and publish.
5. Verify it's possible to add submission.
6. Return to edit mode.
7. Add second form.
8. Add e.g. file field.
9. Submit and publish.
10. Try to add submission to first form.
Actual: It's not possible, pattern validation fails.
Expected: Pattern validation does not fail.

Remarks: Please see attached.
At first it seemed like a problem with date field pattern validation but it turns out the issue is more general. It affects other fields as well (e.g. single line text, file, captcha) - more screen-shots added.