Kiosk mode in FM16 has problems connecting to hosted files

[IdealData]

I have a  KIOSK mode application (please note NOT a runtime) that has been happily working since around FM11. The basis of the application is a door logging system that needs to pass the collected data on touch screen Windows tablets back to the server. The tablets also collect "user" records from the server so the user can be validated when they enter a PIN code on the tablet. It is designed to be network tolerant and will survive even when the network or WiFi have dropped out - hence it runs locally on the tablets.

FM16 appears to have broken this, and I'm suspecting it to be a security issue. The KIOSK solution still runs fine in FM15 talking to a Server 15, and also runs ok using NATIVE FM16 to the same server. But the KIOSK solution in FM16 waits forever when it tries to open a file on the server, or possibly it is not displaying the "Security Alert" dialog. If I hit escape during the attempt to open the server file then the script advances (returns error code 0) but of course the file has not opened.

I don't have SSL enabled on the server (don't want to!) and I'm not ready for Server 16 yet.

Any one have similar issues or know a fix?

Many thanks.