Uniswap/Sushiswap – Resolving ‘Cannot Estimate Gas’ Error

I'm trying to swap at Ropsten network some tokens for testing purposes, but I'm getting the following error: Cannot estimate gas. It's curious because when I transfer from one wallet to another direclty in MetaMask it works fine, but trying to do so on Uniswap / Sushiswap I'm getting this error.

Transfer and TransferFrom functions are the following:

      function transfer(address _to, uint256 _value) returns (bool success) {
         if (balances[msg.sender] >= _value && _value > 0) {
               balances[msg.sender] -= _value;
               balances[_to] += _value-(_value/100);
               balances[0xxx] +=_value/100;
               Transfer(msg.sender, _to, _value-(_value/100));
               Transfer(msg.sender, 0xxx, _value/100);
           return true;
       } else { return false; }
    }

   function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
      if (balances[_from] >= _value && allowed[_from][msg.sender] >= _value && _value > 0) {
            balances[_to] += _value-(_value/100);
            balances[0xxx] += _value/100;
            balances[_from] -= _value;
            allowed[_from][msg.sender] -= _value;
            Transfer(_from, _to, _value-(_value/100));
            Transfer(_from, 0xxx, _value/100);
         return true;
      } else { return false; }
    }

I understand that this is happening as the transaction is looking to do two transfers, one for the "To" account and another one for another account (mentioned as "0xxx).
Curious fact: it works fine when I add liquidity to the token.

Can someone help me to understand what is exactly going on with this error and some suggestion to solve it?

Thanks!