Hey all! Sorry for the lack of images, though I'm sure the issue is pretty straight-forward.
I've found a few similar posts, but mostly they just solve it by adding blur to the reflection. I'm convinced my scene is high enough resolution to support the controlled/static reflection shot that I'm looking for. Yet, no matter what I do, the reflection (the image reflected by the glass material of the environment) always comes out as pixelated / blocky.
I've tried farting around with the HDRI sampling itself - toggling from MIP to SAT. And I can't seem to find any particular setting for reflections in the Physical renderer. So I'm a bit at a loss.
To verify the HDRI res as being a non-issue, I experimented by increasing the distance of the reflected object by exactly 2x away from the camera. Effectively, this should have doubled the res, and shrunk the 'blocks' by half. But it appeared to have no effect. So I'm sure it's something in the reflection setting itself, but I've never actually come across reflection quality settings that I can recall.