Stack too deep after adding an public map to a contract

I have a contract that has a lot of logic. I came to the point when I get Stack too deep exception.
In my search for the reason I came to a thing I can not get my head around.
The contract is way bigger but I copied the relevant part. The thing is how is it even possible that a defined public property effects the stack? And what would be possible solutions?
I already tried compile with and without viaIR.
```
contract PositionRouter
{
using Address for address;
using SafeERC20 for IERC20;

struct DecreasePositionRequest {
address account;
address[] path;
address indexToken;
uint256 collateralDelta;
uint256 sizeDelta;
bool isLong;
address receiver;
uint256 acceptablePrice;
uint256 minOut;
uint256 executionFee;
uint256 blockNumber;
uint256 blockTime;
bool withdrawETH;
address callbackTarget;
}
// Enabling this leads to Stack too deep
// mapping (bytes32 => DecreasePositionRequest) public decreasePositionRequests;
...
}

Start with the reduced PositionRouter example and compare compilation with the public decreasePositionRequests mapping enabled or commented out, both with and without viaIR. Confirm the stack-too-deep failure and determine whether the behavior is expected or indicates a Solidity compiler issue; done means documenting the cause and a supported solution.

Written by the indexing model from the issue text.