z-fighting at a certain connection

tryguy

So, while building, I encountered some z-fighting at a particular connection. I thought you might like to know. I'm not sure what it'd look like if I'd used a normal half-brick for the same purpose. But, this is the result when using a plug. But, note the difference between the full-length columns, at the top. There's no z-fighting there, so I wonder why this is different. Unique combo?

Shatojon

Thank you!