Kodi reduced in UI reduced to quarter size in top left corner after

Hi guys I am hoping someone can help me with an issue i keep having. When I switch my tv back on after leaving kodi (v17.0 problem also occured under v16) running on my win 10 htpc sometimes it is reduced to a quarter size in the top left corner of the screen (not just when playing video). It is solved by changing the system settings > display > Fullscreen to windowed and back again. But it is driving my wife (and me) mad.

the GFX card (AMD Radeon HD 6450) has upto date drivers (15.201.1151)

Here is a paste bin of my log file http://pastebin.com/NtApFe6p

around 9.23 (line 2193) switched the tv back on and had to reset the display properties to fix the quarter screen issue.

Quote:08:59:53.061 T:6248 NOTICE: VideoInfoScanner: Finished scan. Scanning for video info took 00:13
09:23:51.236 T:10752 ERROR: PERIPHERALS::CPeripheralCecAdapter::OnTvStandby – Unexpected [standby_pc_on_tv_standby] setting value
09:23:52.692 T:1408 NOTICE: Found screen: Dummy Monitor on AMD Radeon HD 6450, adapter 0.
09:23:52.725 T:7508 WARNING: CRenderManager::WaitForBuffer – timeout waiting for buffer
09:23:52.757 T:1408 NOTICE: Primary mode: 1024×768@ 60.00 – Full Screen
09:23:52.778 T:1408 NOTICE: Additional mode: 640×480@ 60.00 – Full Screen
09:23:52.781 T:1408 NOTICE: Additional mode: 720×480@ 60.00 – Full Screen
09:23:52.783 T:1408 NOTICE: Additional mode: 720×480@ 59.94 – Full Screen
09:23:52.784 T:1408 NOTICE: Additional mode: 800×600@ 60.00 – Full Screen
09:23:52.785 T:1408 NOTICE: Additional mode: 1024×768@ 60.00 – Full Screen
09:23:52.786 T:1408 NOTICE: Additional mode: 1152×864@ 60.00 – Full Screen

Any help with this would be much apreciated. I am thinking it is to do with the tv being seen as a dummy monitor?