How can uniswapV2Library pairFor addres be different from uniswapV2Factory getPair for same tokens?

I'm writing a Solidity smartcontract. Working on Kovan testnet.

I understood from the Uniswap documentation, that the .pairFor method from the uniswapV2Library contract should return an address for this pair of tokens. For free, since it's not making external calls, it's calculating inside. And that .getPair method on the uniswapV2Factory should do the same, but via a request that costs gas.

However, both methods return a different address, and I can't understand how that is possible. Can somebody explain what I'm missing?

This is my contract (i simplified it a bit), most important is the repl function:

pragma solidity =0.8.12;

import './UniswapV2Library.sol';
import './interfaces/IUniswapV2Router02.sol';
import './interfaces/IUniswapV2Pair.sol';
import './interfaces/IUniswapV2Factory.sol';

contract FlashLoaner {
  address immutable factory;
  IUniswapV2Router02 immutable sushiRouter;
  IUniswapV2Factory immutable factoryV2;
  address public var1;
  address public var2;
  address public resultPair;
  address public resPair2;
  address public fact;

  constructor(address _factory, address _uniRouter, address _sushiRouter) public {
    factory = _factory;
    sushiRouter = IUniswapV2Router02(_sushiRouter);
    factoryV2 = IUniswapV2Factory(0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f);
  }

  function repl(address _sender, uint _amount0, uint _amount1) external {
      //0x052AE8b0F7E5c610937920e46ED265c2063Cb7B8 = uniswapV2pair WETH RAI
      address msgsender = 0x052AE8b0F7E5c610937920e46ED265c2063Cb7B8;
      
      IUniswapV2Pair v2Pair = IUniswapV2Pair(msgsender);
      address token0 = v2Pair.token0();
      address token1 = v2Pair.token1();
     
      //uniswap v2 factory address
      fact = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f;
      //results in 0x3c8B7Cf2bDCC9DEB44a72f40052ae8b0F7E5C610
      //which i don't understand??
      resultPair = UniswapV2Library.pairFor(fact, token1, token0);
      
      //results in 0x052AE8b0F7E5c610937920e46ED265c2063Cb7B8 = uniswapV2pair WETH RAI
      //which makes total sense
      resPair2 = factoryV2.getPair(token0, token1);
      
  }

  
}

Why is resPair2 not the same as resultPair??