Why does this value turn nil when I pass it into a function?

So in my script, I call seperateCFrame and it ends up giving me an error on the loop because it's trying to find the length of a nil object (cfrm) thinking its a string. When I do a print test on it I find that before I call the function it prints fine, but as soon as I call it the parameter turns nil. Why is that?

function seperateCFrame(cfrm)
    print(cfrm)             -- Prints nil
    local localSeperator = ","
    local element = ""
    local newCFrame = {}

    for i = 1,string.len(cfrm) do   -- Error trying to get len of nil value
    -- Other stuff...

local data = serverdata
    for i,v in pairs(data) do
        print("Test: "..v," | ",v[3])   -- Prints everything fine
        local cframe = seperateCFrame(v[3])
        -- Other stuff...