That file looks fine, as you thought.
The error points to
`Invalid character after parsing property name. Expected ':' but got: ,. Path 'clan', line 29, position 13.`
That makes sense to me because line 29 it's right before 'losttitle' which, in older versions of PlayerRanks, had the variables backwards.
"clan": "Clan",
"tooktitle": "{0} has taken the title {1}.",
"losttitle": "You have lost the title {0} to {1}.",
'losttitle', is the one that is wrong in most people's lang files,
so perhaps someone tried to fix that at some point?
Now that your file is working fine the fix for incorrect var placement would be to swap 0 + 1 in "losttitle"
like this
"clan": "Clan",
"tooktitle": "{0} has taken the title {1}.",
"losttitle": "You have lost the title {1} to {0}.",
I have fixed this in PlayerRanks plugin but lang files don't automatically update changes for already existing entries,
leaving users to fix it manually.
Alternative, if your lang file is totally unmodified, you could just delete it then reload the plugin.
PlayerRanks will create a brand new file with the correction already in it.