Opaque faces sometimes not rendering when behind transparent object? (OpenGL 4.5)

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If you can't see the image, the issue is that sometimes faces behind transparent faces don't get rendered.

I'm trying to make my voxel game as fast as possible. I just got into transparency.

I've done some research about this issue, and a bunch of people are either not very clear on their solutions, or tell me to put transparent objects in a separate mesh than normal, opaque objects. However, when I tried this, I got absolutely terrible fps, so that isn't an option.

I want to know if there's a solution that's good fps, keeps depth testing, and allows for transparent and opaque objects to be in the same mesh.