Hello,
I have a query are you using lead time scheduling in your MRP ?
The work center settings should override the factory calendar settings and you should not have a planned activity in the work center on non working days defined in the work center calendar but that is when you use lead time scheduling in your MRP.
Also have you done this setting at your work center ? It should be 0, in your case as you have defined extra non working days in your new calendar.
Please check the below threads explaining the same problem,
Factory calendar in work center
Please check and revert.
Best Regards,
Ameya B.