Issue with Margins on Artboards in Illustrator

I'm currently facing an issue with artboards in Adobe Illustrator and could really use some help and guidance from the community.

The problem I'm encountering is that my artboards have unwanted margins, which seem to behave differently across my various artboards. Let me clarify that these are not guides or bleeds causing the problem. On one particular artboard, the margins appear to match up perfectly, but on another one, they seem to try and mimic the size of the first artboard.

I've tried double-checking all my settings and configurations, but I can't seem to find the source of this inconsistency. I've also ensured that my artboards are correctly set up, without any unintentional hidden elements that might be affecting the margins.

Has anyone else experienced a similar issue in Illustrator? If so, I'd greatly appreciate your insights on how to troubleshoot and resolve this problem. It's quite frustrating and impacting my design workflow.

Thank you so much for your time and assistance in advance. I'm looking forward to your expertise and feedback!