Sky getting cropped for no reason!

New in Davinci Resolve.
Was trying to do a simple sky replacement in Fusion. But whenever I apply any effect node (like mirror or gaussian blur) to my background sky, it gets cropped for no apparent reason.
I have attached a screenshot with the issue marked in red (upper left corner of each image)
Please someone help!

I can’t say for certain but maybe there is something going on with the way that the ResolveOFX are handling domains.
What happens if you don’t use the Resolve tools but Fusions native Blur or Transform tool to flip the image?
To be sure that you are using native fusion tools right click in the Flow and select Add Tool>Blur>Blur.
The Resolve tools should be in their own folder.

And change your order of operations. If the blur is after the PlanarTransform, it will be blurring what's actually on the screen at that point instead of blurring pixels that have been moved out of the raster, which is inefficient.

Blurs usually crop the image to the frame for just that reason, and if you then have a second transform trying to pull the out-of-frame pixels back into the picture, they've been discarded. Fusion's native Blur node has a control to clip to Domain instead, or turn off clipping entirely, but it's better to simply change the order of the nodes.