We experienced this problem in the apps that we created using the basic viewer template:
if you are editing a feature service (editor panel active and attribute popup open) and you use one of the measuremenet tool (Area or lenght), the edi pop up closes and after closing the measurement widget yo can't do no more edits beacuse you can only open the popup in view mode.
we did't add any customizatione to the template, only some look and feel touch (logos and color) .
any info, suggestion or workoround is very appreciated
thank you
enrico