I use the Addons Linker and its a great tool especially when it comes time to do an MFS update, however you can experience an issue with .json files being locked. I have examined this and found it to be caused by the developers deliberately changing the ownership of all files in the Community Folder that have been loaded at least once by running the sim. The “big” issue is that this means that even third party purchased addons have their file ownership changed (locked). This seems to be only an issue with .json files.
I have not found a way to regain ownership of these files, so the immediate answer is to never let MFS get to them in the first place. Therefore if you install third party addons and you can’t prevent them from being installed in the default CF, make sure you don’t run the sim.
Move the addon out to your Addons Linker CF first. Otherwise the only way to fix any addon that has had it’s ownership “locked” is to re-download it or at least unzip it again if you have kept the original .zip file.