nested multi-cam zooms (scales up) on playback

I have a nested multi-cam sequence with differing file types from different cameras all recorded 1080 60i. I'm having problems with the track recorded on a JVC GY-LS300CHU as 1920 x 1080 in Quicktime 422 yuv.

When I set the display mode to multi-cam, this track zooms in when I play it back. I can get it to stop doing it for a while if I set it to High Quality Playback, but after some time, it goes back to doing it again. I've tried disabling all effects (motion and otherwise) on both the underlying sequence and the multi-cam sequence. I've tried reducing the playback resolution, unchecked the "Show Multi-Camera Preview Monitor," changed the Video Rendering Playback Engine, cleared cache and It still does it.

Anyone ever come across this before? Any suggestions on what may be wrong.

Here are my computer specs:

Windows 10 Pro 64bit

intel core i7-3930k 3.20 GHz

RAM: 32 GB

OS: on a Crucial CT256 SSD

video files on a SanDisk SSD (SDSSDXPS480G) 480GB

Video card: NVIDIA GeForce GTX 570 with the latest drivers; 1280 MB 320-bit 0.5ns GDDR5 memory.

Thanks.

Wally