In upgraded Istanbul Express instances, the Form Designer takes about 15-20 seconds for the page and fields to load, and then when saving the form, it might take 15-20 seconds to complete as well. The normally expected time would be a maximum of 5 seconds.
Steps to Reproduce
Log in as admin to a demo Express instance.
Navigate to Incidents > All and select an incident record.
Right-click on the header and select Configure > Form Design.
The form displays but the Fields and Field Types take some time to load.
Make a change to the form and click Save.
Note how long it takes. If you have worked in the Helsinki release, note that the time required is longer when compared to that release.
This problem is fixed in the upcoming Istanbul Patch 5 and Jakarta releases. While an upgrade is not possible yet, the workaround is to use the Configure -> Form Layout option instead of the Form Design.
Related Problem: PRB732410