Hi and welcome to the Chiari forum.
Do you notice a pattern to your new heaadaches? Surgery can lessen symptoms, but it may not get rid of them.....and it is possible to have them return and there could be several reasons why they would reoccur.
Scar tissue could form at the incision site and cause a CSF obstruction.
Try to see if there is a pattern, some of us do get headaches still after surgery and sometimes it can be weather related, or due to stress,.
So do try to see if there is a pattern, keep a journal of sorts this may be helpful to see what might be the reason,
Also when did these start?