FileMaker Server 18.104.22.168
FileMaker 13 - various versions
Windows 7, Mac OS X 10.11.5 El Capitan
Mostly Dell PCs meeting the suggested specs, also Macs. Server is on a new Dell Box considerable exceeding the spec for FMS15.
We had an onTimer routine that ran without problem under FileMaker Server 14. When we switched to FMS 15, the behaviour of the onTimer script changed. The routine runs in a hidden, off-screen window. The first step checks to see what layout the user is on. Previously, the onTimer window remained hidden, but now it is brought to the front and made visible as soon as the script is launched.
It is easy enough to get around this by removing the check for layout because the change of behaviour means it does not matter which layout the user is on (although it might be slightly inconvenient if they are acting on the result of the script).
I repeat, this is a change of behaviour between FileMaker Server 14 and FileMaker Server 15.
The behaviour seems to be independent of version of Pro or platform of the end user
How to replicate