$ cvtsudoers -V
cvtsudoers version 1.8.25p1
cvtsudoers grammar version 46

$ cat sudoer-bad-json
Cmnd_Alias      CMDA=/path/to/cmda
Cmnd_Alias      CMDB=/path/to/cmdb
%user           ALL=CMDA,CMDB

$ cvtsudoers -e -f json sudoer-bad-json 
{
    "User_Specs": [
        {
            "User_List": [
                { "usergroup": "user" }
            ],
            "Host_List": [
                { "hostname": "ALL" }
            ],
            "Cmnd_Specs": [
                {
                    "Commands": [
                        { "command": "/path/to/cmda" },
,                        { "command": "/path/to/cmdb" }
                    ]
                }
            ]
        }
    ]
}


note the rogue common at the beginning of the 2nd command line