I have the same problem. On latest public version of Windows 10 and latest RCT2. I own RCT2 through Steam and have full screen turned on.  
	]Processor    AMD Ryzen 7 3750H with Radeon Vega Mobile Gfx     2.30 GHz 
	Installed RAM    16.0 GB (13.9 GB usable) 
	System type    64-bit operating system, x64-based processor 
	 
 
	Latest public version of OpenRCT2.