Very occasionally, cannot open select boxes in the channel editor menu bar

Sometimes the alter-ego, device and projects select boxes cannot be opened. Unfortunately there is no stable reproduction path to demonstrate the issue. Furthermore there are no console errors, nor any server-side error/warning logs.

As a work-around a user can manually reload the iframe to make the select boxes work again.

Example of a scenario where I ran in to this issue (enterprise-hap):

Precondition: there is at least one project associated with the "Hippo Acceptance Project" channel.

• login as admin
• open channels perspective
• click "Hippo Acceptance Project" -> Core "project" is selected by default
• open the "projects" select box and select a project
• project is selected

Expected: alter-ego, device and projects select boxes can be opened to select another item. Actual: all three select boxes are unresponsive and cannot be openend.

"Stable" reproduction path for Chrome

• Start up a clean hap enterprise
• log in into the console
• import vWAsi.xml under /hippowpm:hippowpm/hippowpm:projects
• delete /hst:hst/hst:configurations/hap-preview
• save changes
• import hap-vWAsi-preview.xml , hap-vWAsi.xml and hap-preview.xml under /hst:hst/hst:configurations
• save changes
• log in into the cms
• open the channel perspective
• toggle a few times between 'Core' and 'AJ' until the select freezes.