Sometimes you won't get access to repair permissions from Disk Utility on a certain disk partitions. The button is just grey.
Leave Disk Utility.
If you right click on the drive from your desktop you get a context menu and can select "get info".
On the bottom you have a chapter "sharing & permissions".
Ignore ownership for that volume should be ticked.
Klick on the keylock, enter your PW, unselect the Ignore Ownership.
You will be able to repare permissions now.

RIN67630