Why are the edges of the corners of some of my objects curving off after I render? So I’m making a low res PS1 style scene, and a couple of the objects in my scene have their edges curve off after I render the scene, such as the checkered floor here -

However sometimes it fixes itself after I go straight from edit mode of that object to render mode ? This is how it should look -

Could anyone tell me what’s causing this or how to fix it ?
Thanks !
It looks like you're using a Subdivision Surface modifier with the viewport level set to 0.

When rendered with the Catmull-Clark algorithm this adds extra faces based on the Render setting and interpolates their location.