What type are we talking about?
Generally: when the FD does not display what the crew wants it to for whatever reasons, it is best not followed; subsequent actions depend on situation. Also when flying the approach on other systems like a HGS that generates its own flight director which on occasion differs a fair bit from the PFD F/D especially during the capture phase, it is obvious that the HGS-generated F/D is the one to be followed and the one displayed on the PFD is advisory at best.