Break mode and Immediate Window results are different - ms-access

Question

I am using MS Access 2016, Windows 10, USAF Laptop running SDC.
I am having an issue with debugging some code. When I hit a line in Break mode I get a Run-time Error '13':Type Mismatch, When I run the exact same code outside of break mode, the code functions properly.
Here is the basic code that is causing me problems:
Private Sub btn_ReqKey_Click() 'This is not all of the code only those lines that are necessary
Dim trgt_CACID as String
Dim Temp_KeyCode as String
trgt_CACID = Me.CACID.Value 'Pulls value from short text field of "1234567890"
'Here is the issue
Temp_KeyCode = UnlockCode(trgt_CACID) 'Run-time Error '13': Type mismacth
More code
End Sub
Public Function UnlockCode(ByVal CACID as String) As String
lots of code that generates a 25 digit Alpha code
End Function
When I click on the button the code fails at "Temp_KeyCode = UnlockCode(trgt_CACID)" Run-tine Error '13': type mismatch.
However, if I reset the code execution and run this in the immediate window without pressing the button.
trgt_CACID = "1234567890"
?UnlockCode(trgt_CACID)
Returns the proper code without throwing an error. So the function UnlockCode() works properly, just not at execution.
Additionally, When in break mode from pressing the button and I attempt the same line of code in the immediate window, it returns the same run-time error '13': Type mismatch.
Furthermore, I exit Break mode, reload the variable and execute the same line of code it works again.
So I know something in the execution environment is being affected, I cannot figure out what that is. This is the first time I have seen a disparity with how the immediate window functions as compare to code execution.
Side Note/Quirk, in the immediate when I enter the function, the helper pops up to guide me for the variables required. When I type the same in the module code, the helper pop ups do not display. So weird. Right? Further evidence something is different between the two environments.
Any help or assistance would be greatly appreciated.
Thanks in advance.
KO

Answer 1

Based on the discussions with Erik A and Gustav, I changed the Function name that was having a conflict with a table field name I was using. Once I changed everything to be dissimilar: table Field Name, Form Textbox name, and Function being called. Everything worked fine. So apparently the context I was calling from already had something using the name of the function and that field name was being picked up and sent to a function with the same name as the field. This created a subtle conflict that explains the disparity between execution in the context of table and form and when being Manually called in the Immediate Window AND why it worked in the Immediate window, but not during execution. Thank you Erik A and Gustav for their assistance.

Answer 2

Try running it with a dummy function:
Public Function UnlockCode(ByVal CACID As Variant) As String
UnlockCode = String(25, "0")
End Function
If that runs, debug your secret function.