Steps to add more than two roles?
{
  "Sync Nicknames": false,
  "Sync Data": [{
    "Oxide Group": "Default",
    "Discord Role (Name or Id)": "Server Member",
    "Sync Source (Umod or Discord)": "Umod"
  }, {
    "Oxide Group": "warlord",
    "Discord Role (Name or Id)": "VIP",
    "Sync Source (Umod or Discord)": "Umod"
  }]
}
{
  "Sync Nicknames": false,
  "Sync Data": [
    {
      "Oxide Group": "Default",
      "Discord Role (Name or Id)": "Server Member",
      "Sync Source (Umod or Discord)": "Umod"
    },
    {
      "Oxide Group": "warlord",
      "Discord Role (Name or Id)": "VIP",
      "Sync Source (Umod or Discord)": "Umod"
    },
    {
      "Oxide Group": "third",
      "Discord Role (Name or Id)": "3rd",
      "Sync Source (Umod or Discord)": "Umod"
    }
  ]
}

So that's the issue I have. Anytime I have more then 2 of those this happens.

[Discord Core Roles] Message: Removing player PrinceOfCookies(76561198947126693) from discord role VIP(745948556828999723)
[Discord Core Roles] Message: Removing player PrinceOfCookies(76561198947126693) from discord role VIP(745948556828999723)
[Discord Core Roles] Message: Adding player PrinceOfCookies(76561198947126693) to discord role VIP(745948556828999723)
[Discord Core Roles] Message: Removing player PrinceOfCookies(76561198947126693) from discord role VIP(745948556828999723)
[Discord Core Roles] Message: Removing player PrinceOfCookies(76561198947126693) from discord role VIP(745948556828999723)
[Discord Core Roles] Message: Adding player PrinceOfCookies(76561198947126693) to discord role VIP(745948556828999723)
[Discord Core Roles] Message: Removing player PrinceOfCookies(76561198947126693) from discord role VIP(745948556828999723)
[Discord Core Roles] Message: Removing player PrinceOfCookies(76561198947126693) from discord role VIP(745948556828999723)
[Discord Core Roles] Message: Adding player PrinceOfCookies(76561198947126693) to discord role VIP(745948556828999723)
[Discord Core Roles] Message: Removing player PrinceOfCookies(76561198947126693) from discord role VIP(745948556828999723)
[Discord Core Roles] Message: Removing player PrinceOfCookies(76561198947126693) from discord role VIP(745948556828999723)
[Discord Core Roles] Message: Adding player PrinceOfCookies(76561198947126693) to discord role VIP(745948556828999723)
[Discord Extension] Discord ratelimit reached. (Ratelimit info: remaining: 0, limit: 10, reset: 1600499405, time now: 1600499395

Can you please set this line in your config like this: "Debug Level (None, Error, Warning, Info)": "Info" and then give me the output from the console.

Also, paste your config here so I can take a look.
Its a bug if i had to guess with the plug-in where only 2 can be used at once.
{
  "Sync Nicknames": false,
  "Sync Data": [{
    "Oxide Group": "Default",
    "Discord Role (Name or Id)": "Member",
    "Sync Source (Umod or Discord)": "Umod"
  }, {
    "Oxide Group": "warlord",
    "Discord Role (Name or Id)": "VIP",
    "Sync Source (Umod or Discord)": "Umod"
  }, {
    "Oxide Group": "vanilla",
    "Discord Role (Name or Id)": "VIP",
    "Sync Source (Umod or Discord)": "Umod"
  }, {
    "Oxide Group": "renegade",
    "Discord Role (Name or Id)": "VIP",
    "Sync Source (Umod or Discord)": "Umod"
  }]
}​

https://pastebin.com/myyNaKmz
I need you to set the debug level to "Info" in the config so we can see what's going on.
[Discord Core Roles] Info: Processing Discord for Raagnoack (76561198262162000) Is Leaving False
[Discord Core Roles] Info: Checking player Raagnoack (76561198262162000) Discord: 371049800747057153
[Discord Core Roles] Info: Processing Oxide for Raagnoack(76561198262162000) Discord ID: 371049800747057153 Is Leaving False
[Discord Core Roles] Message: Removing player Raagnoack(76561198262162000) from discord role VIP(745948556828999723)
Can you add me on Discord MJSU#0814 so we can look into this further with some debug builds.