Please make a backup of your project before following.

Right click the BP_MasterLock and select Create Child Blueprint Class and name the new blueprint BP_KeyLock.

Next go to the BuildPartList and create a new row and copy the image below.

Next go to the BP_MasterBuildPart and create a new variable called OnlyOneOwner and set the variable type to Boolean and tick Instance Editable.

Next will depend on your project, for a default project go to the BP_BuildingMenuPageThree and select None_07 widget in the hierarchy panel, then in the details panel set it like the image below.

Now click the save all button in the content browser and close the project.

Add the highlighted nodes shown in the image below, location at the top of the image.

Now download and unzip the files linked below and copy the video.

https://www.dropbox.com/s/kqa7q9okqtz4vmx/PBSV2%20KeyLock.zip?dl=0

Only the owner can lock/unlock the key lock by looking at the lock and pressing E. When locked only the owner can open and close the door/window. When unlocked any player can open and close the door/window.