Just a short post in case anyone is also struggling with a couple of bugs in 4.30 preview 4.
1. If you display an identity field on your form, and the picture displays with a "," for thousands separator, then you cannot save the form.
The URL is malformed and includes the "," which makes the database believe you're trying to change the identity field.
e.g. if PRE:IDFIELD = 9,999 then this shows as part of the URL &PRE_IDFIELD=9%2c999
2. If you have a checkbox, and the checkbox has a READONLY condition, then it is impossible to turn the checkbox off.
Regards,
Alan