This is something that has plagued me for a while.
After a while of working on apex.oracle.com I get this error:

and I can't continue.
If I clear my cache it works again for a short while but then happens again.
If I work in an incognito browser it is fine (all the time).
This is probably a ‘me’ issue but has anyone encountered this and found a way to sort?
It happens on Oracle University to me also.
No issues on any other non-Oracle sites.
Very frustrating.