ssl mixed content error intraweb 15.1.5

[PDSBILL]

Also if you deploy your apps locally on your own dev machine, what is the result?

OK, this is just getting stranger and stranger.

Using Delphi 10.3.2  IW 15.5.1
The test program fails at my customer site when accessed outside their network (SSL and non SSL). But works inside there network.
The test program works at another customer site when accessed both inside and outside their network. SSL and non SSL
The test program works at our office site when accessed both inside and outside our network. SSL and non SSL

when run, the first form is shown with single button.
When AsyncClick event of button is executed  the 2nd form is to be shown (TFrm2.Create(WebApplication).SHOW);
The program freeezes, does not show the next form and we get the browser error in debugger
 requested an insecure resource 'http://10.10.250.38/webPPReviewer_DEV/projectestssl.dll/q19he8KSL-L7KEbcSSt18o6hYSq/'. This request has been blocked; the content must be served over HTTPS.

Using Delphi 10.3.0  IW 15.0.17
The test program works at both customer sites when accessed both inside and outside their network.

It appears that something is redirecting the baseurl to 10.10.250.38. I am would blame this on my customers firewall, but why does it work under 15.0.17 but not under 15.1.5.
Both customers are running same IIS server version 8.5.9600 on windows server 2012 R2
Both a running with dedicated App pools for the test app.

Any idea's ????

Bill B