glm and lm can't find weights

Hello, and apologies for not providing an example. However, my question is
more general.

I have a lengthy function. This function is using another internal function
that modifies the data frame I am reading in. This internal function is
using the command model.frame (with data and weights inside) and returns a
data frame I am using for further analyses.
However, when I try to run my function (which has an lm or a glm  commmand)
using that new data frame and separately defined weights, I get an error:
can't find your weights object.
This happens despite the fact that I actually print the weights object
right before the glm command. The object is there - I can see it using
ls(). I checked and rechecked - there are no typos.
Interestingly, this happens only when I run it as a function.

When I rename my arguments, go inside the function and run it line by line
- I don't get this problem. Clearly, something is happening with my weights
in the function environment. I was thinking - can it be that once I've used
model.frame - everything else - like glm and lm - is confused as to what
the weights are and doesn't want to take the weights I hand over to it but
is looking for them elsewhere?

Thank you!
Dimitri