I am trying to update the collaboration permissions of one of my groups (id: 32506251) and with the Owner user the window for assigning permissions to roles stays blank.
I also had the same problem for a long time and the solution was to change my Roblox Studio language to English after i noticed some reports had their studio language set to Portuguese (or Spanish).
I find it weird because this was only happening to games hosted under my group, and collaboration settings on other games appeared normally in Portuguese. I assume its a localization issue?
If this is still occurring to this day, submit the error log and other relevant details to @Bug-Support. There was an existing bug about this, but it was more recently closed as not being reproducible.