Describing the issue: A custom form to collect event data in a tracker program, when data elements are compulsory from the program design it works fine (tracker app stopping complete when missing), however when we try to make other data element compulsory using rules (based on previous data element values), we can still complete the program even when the data element is missing, like the rule is not working. If we remove the custom form, the rule works as expected.
As additional information, I found a couple of JIRA tickets related to this ([DHIS2-9624] - Jira) where they have reproduced the issue in play instances. As you can see there bug is reproducible in 2.34 as well. The ticket is really old and marked as TODO, however is unassigned.