My monsters skills when in extra have both gained and reduced by 2.

You’re using the Beyond20 extension, try turning that off and see if it fixes it.

Ignore my previous answer. When a monster is loaded as an Extra like that, they system calculates the skills based on PB and relevant Ability Score regardless of whatever was entered in the content creator.

Thats a shame. Then you can't give familiars certain skills proficiencies. How weird.

It’s because they were trying to make Extras be dynamic to implement things like Steel Defenders and Homunculous Servants, but the hat proved to be to daunting a task and they’ve abandoned that pursuit for the time being and have redirected their focus on getting ready for 2024’s new edition.