Windows 10 Remote Desktop alt tab/Win+M problems

I basically don't use my own desktop to do the majority off my work, I RDP out to customers systems and work there. I tend to maximise the RDP session on to one of my screens and work exclusively within the RDP session.

What I've been struggling with since I installed Win 10 is that all the windows control function will sometimes not operate on the remote machine.

• Pressing the Win key will bring up the start menu on both local and remote system
• Alt + Tab flicks me back to my local running programs, no the ones on the remote system
• Win+Cursor keys mess with the RDP client window, not the windows running within the RDP session

I'm not convinced that this is specifically a Windows 10 issue, there are posts here that indicate the same issues going back to windows 7 (here)

However I never experienced this in previous versions of Windows and its driving me nuts.

• I have tried deleting and recreating my .RDP shortcuts.
• I've tested with 'Apply Windows Key Combinations' set to 'On the remote computer' or 'Only when full screen', neither make a difference.
• I'm RDPing from Win 10 (build 10240) to a variety of Windows versions including Server 2003 r2/Server 2008 r2/Server 2012 R2/Windows 7/8. There doesn't appear to be any consistency as to which ones are OK and which ones are not.
• I am exclusively RDPing to virtualised [ESXi] guests, not that that should make any difference

EDIT : For what its worth I've updated to build 10586.29

EDIT 2 : I've tracked it down to Synergy.