if I use append_hf() for adding my custom header to initial request, how I can remove this header later ?

What I'm doing:

1) initial request: remove RPID header with remove_hf

2) initial request: add custom RPID header append_hf

3) after rerouting: in failure_route remove RPID header remove_hf

4) after rerouting: in failure_route add custom RPID header with append_hf

The result of this, are 2 RPID headers, because remove_hf did not catch RPID header added in step 2, but I think the original one that was removed already in step 1.

Thanks,

Mino