It's my turn to get this dreaded message (on apex.oracle.com). The page doesn't want to load in APEX Builder after the last change to a Template Component. The error in the console:
Uncaught TypeError: Cannot read properties of undefined (reading 'length')
at i (pe.model.min.js?v=24.2.2:4:23738)
at s (pe.model.min.js?v=24.2.2:4:24264)
at p (pe.model.min.js?v=24.2.2:4:28448)
at re (pe.model.min.js?v=24.2.2:4:28839)
at pe.model.min.js?v=24.2.2:4:131090
at Object.initModelConfig (pe.model.min.js?v=24.2.2:4:131613)
at Array.<anonymous> (f4000_p4500.min.js?v=24.2.2:4:15526)
at c (desktop_all.min.js?v=24.2.2:5:28402)
at Object.fireWith [as resolveWith] (desktop_all.min.js?v=24.2.2:5:29150)
at desktop_all.min.js?v=24.2.2:5:31343
The only thing I could do was Export As of … and import the app again.
Maybe the APEX team can do something with this JS log.
So far, I narrowed it down to: it happens when I add an Action Template that is probably an invalid template.
Now, on first try, that is very likely to happen. However, you want to be able to see the result of that invalid template, not a hanging page load.