Wrong WM_LBUTTONUP message on RemoteApp

So we have a problem with one of our programs (we are the developers). The program is VC++ with MFC, if that helps.

This program works great on both local or normal RDP sessions.

But *only* when on a remoteapp (remoteapplicationmode:i:1) we get this very bizarre problem:

In one part of our program, even when you hold the left button (WM_LBUTTONDOWN) you get immediately a (WM_LBUTTONUP)

I checked our code and cannot find anything that would do that, and the fact that it only fails when in remoteapp mode, makes me think there must be something different when handling messages in this mode.

We have 2012 servers up to date and Win8.1 client up to date too, but we can reproduce in different servers and clients.

Any ideas of what we may be missing here?

Thanks

DCProven