Symptoms

Alerts custom fields are being cleared out when the Alert is reopened

Release

All releases

When you click ‘New’ button, Designer loads all fields (non-system) on Alert table and place them under Transform and Compose Alert Output tab.
The Custom fields are left blank by default and so are some of the OOB fields.
Onload, all fields are marked as not dirty (not modified) on client side.
When user save the rule, backend logic loops over all form elements and check to see if they are dirty (modified). An em_compose_field record is created for each ‘dirty’ element.
If a field has data and then blanked out, then an em_compose_field record will be created, mapping the value for that field to a blank value. Similarly, if a field has no value and a value is entered and and then removed. The field is still marked as dirty and an em_compose_field record with blank value mapping is created as well.

Note: If the Alert is reopened, the value of those fields will be blanked, due to this mapping.

Remove the record from the em_compose_field which has a mapping to those blank fields.