When using PPSSPP with the vulkan renderer, the video output becomes a tiny window at the top left of the screen. openGL does not have this problem. Changing the resolution through the core does not fix the problem. Screenshot and log below.
Did you close content and re-open after changing the option?
I did. After every change I closed the core and RA itself. The problem still persist once I ran a game again. The screen size does increase with the setting but it is still off-center and does not scale to the screen.
I have the same issue. Works well with GL. With Vulkan I get a tiny screen on the top left as shown in the first post.
i also have the exact same problem. works with gl, but vulkan puts it in the top left corner also
any ideas are welcome 
Same here. I switched from standalone PPSSPP today and encountered this very same issue.
I just updated my PPSSPP core from the one released 2019-02-07 to 2019-06-12 and now it just crashes with Vulkan. So I’m sticking with my old version witch works great with Vulkan.