Getting a execution reverted message: code: -32000 calling a new function

I'm banging my head against the wall with this problem:

When I supplyLiquidity and using the contract's address for onBehalfOf, I can later approve the contract address on the WETH gateway and withdrawLiquidity no problem. Works every time.

function supplyLiquidityContract() external payable{
       address onBehalfOf = address(this);
       WETHGateway.depositETH{value: msg.value}(pool, onBehalfOf, 0);
   }
   function withdrawlLiquidity() external{
       uint256 balance = AaveWMatic.balanceOf(address(this));

       AaveWMatic.approve(address(WETHGateway), balance);
       WETHGateway.withdrawETH(pool, balance, address(this));
   }

If instead I supplyLiquidity using msg.sender as onBehalfOf, and later transfer that aToken to the contract, I should then be able to withdrawLiquidty from the contract the same as before, but it consistently reverts, even though everything from approvals to aToken balance on the contract appear to be right.

revert message is 
"code": -32000,
"message": "execution reverted"

am I missing something? why would it matter if the contract's Aave tokens came from a transfer from another account first instead of directly with supply liquidity?