CK II - Great Fortress defends foreign holdings in province

[Chep]

One line summary of your issue
Great Fortress defends foreign holdings in province

Game Version
3.1.1

What expansions do you have installed?
All of the above

Do you have mods enabled?
No

Please explain your issue is in as much detail as possible.
I just found out that the Great Fortress/Castle protects foreign holdings in my province from me. But not only that (which is already pretty stupid on it's own), it also gets damaged when I siege down said holdings.

Steps to reproduce the issue.
build a great fortress. have one holding owned by foreign power/be independent. attack said holding.

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[Kurblius]

That's pretty funny actually. Though I'm sure it's no fun to discover!

 

[Chep]

yeah it's pretty annoying when you have to wait 14 years for the fortress to be repaired and in the meanwhile you suffer all those maluses (like being over your court size) because you no longer have the bonuses from the great work :/