For several years I’m using some personal software to control Fsx from a remote computer en to connect it to Google Earth. I’ve had some problems in the past with the SimConnect.dll that is used heavily by the software.
Since SimConnect.msi v10.0.61259.0 which installs version 10.0.61637.0 of Microsoft.FlightSimulator.SimConnect.dll (never understood why the version numbers don’t correspond) I haven’t had any problems. Even better: my software connected flawlessly to P3D and to FSX:SE. I’m not sure if the same would happen using only the SimConnect.dll provided by P3D or FSX:SE, but for those who encounter problems with SimConnect it could be worth trying the installation of the version I mentioned.
The installer SimConnect.msi v10.0.61259.0 can be found in de folder C:\Program Files (x86)\Steam\steamapps\common\FSX\SDK\Core Utilities Kit\SimConnect SDK\LegacyInterfaces\FSX-XPACK (if you ran a default installation of FSX:XE).