What Go Nogo gage to use for M5 internal thread after Plating?

Dear Reader,
I have a specific problem. My Organization is procuring parts from external source. This is a threaded part (M5 internal thread), which is subsequently plated (Zn plating).
We are facing problems that the M5 Go gage is not answering after plating. Before plating, the thread answers the Go gage.
Do I need to provide a special plating allowance in the thread tapping sequence?
Do I need to use a different gage for the check after plating? I am told that vendor had a Type G and Type H gage.

Dear

According to me, you must have undercut to compromise for plating thickness. This is what most do for zinc plated hardware. You can't change gage nor you can afford that bolts will not fit in standard tapping. So use same gage but while making bolts before plating, change outer and pitch diameter slightly.