Chris,

Once you enter the code,
is that it, or do you then hit the IDENT key, even if not requested?


The AIM (and the German AIP, for that matter) is crystal clear on that:
NEVER hit ident unless the controller tells you to. Also, do not switch
the transponder to standby when changing codes.

You're not necessarily helping the controller by making your radar
return go blink or bloom (depending on equipment) without him/her
expecting it. Instead, it will cost valuable time to deal with the
confusion.

--
Thomas Borchert (EDDH)