Reproducible bug: custom field disappears

Hi

Clicking on the “Update” button within the “Edit Event” form can remove previously added custom fields:
1) Select an existing event
2) Scroll down to “Add New Custom Field:” and select a custom field
3) Set “value” to “test” (or any other value; do not leave value empty)
4) Click “Add Custom Field”
5) Click “Update”
6) Navigate to the list of all events
7) Select the event you just edited
8) The that the custom field you added is gone

Do exactly the same but SKIP #5:
You will see the custom field did not get removed.

Another observation:
1) Select an existing event
2) Make changes to the value of a custom field
3) Click “Update” below the custom field
4) Click the event’s “Update” button
5) Note that the value of your custom field contains the value from before