This is a bug in TurboTax's error checking. TurboTax does not permit code L to be combined with code 7 even though it's permissible based on the instructions for Form 1099-R.
As ColeenD3 indicated, a reasonable workaround is to omit the code 7 and select only the code L. Code L has the same meaning and effect with or without the code 7.
