I don’t think I understand the problem well enough. This is a general function feature/trap.
Functions bindings include the surrounding bindings. In a top-level function, that’s the other top level bindings in the namespace. In a second level function, it will take the bindings of the enclosing form as well. It’s a feature. It can also yield unexpected results.
The general rule is to check the bindings visible to the function. It may be you are using an unexpected binding.