If you think that's a bug, feel free to report it on the bug tracker.
By the way, there's not much difference between OpenGL and Vulkan for NVIDIA GPUs. Unlike games, there's not a lot that can be improved by using a newer API, especially when OpenGL is already very fast and optimised in NVIDIA's proprietary drivers. I'd suggest just sticking to OpenGL for the moment if you have an issue with Vulkan.
edit: to clarify, I'm saying that if you notice a bug, you should report it on https://bugs.dolphin-emu.org so that it can get fixed, which really helps for new backends. But in the meantime, you can fall back to OpenGL which won't be much slower on NVIDIA.
By the way, there's not much difference between OpenGL and Vulkan for NVIDIA GPUs. Unlike games, there's not a lot that can be improved by using a newer API, especially when OpenGL is already very fast and optimised in NVIDIA's proprietary drivers. I'd suggest just sticking to OpenGL for the moment if you have an issue with Vulkan.
edit: to clarify, I'm saying that if you notice a bug, you should report it on https://bugs.dolphin-emu.org so that it can get fixed, which really helps for new backends. But in the meantime, you can fall back to OpenGL which won't be much slower on NVIDIA.