Hi,
Thanks for the quick reply, the solution has been working for more than a year, so there's no new feature required here.
Something has changed last week either from MS or AWS side but unfortunately both aint got a clue, what it is that has caused this. We've engaged both MS and AWS in professional capacity but no resolution so far both blaming each other.
We're going to remove ALB authentication and do our own auth as our site is down for last 7 days because of this.
If you google you'll find tons of questions/issues people have raised on this issue.
Thanks for your help though.