Hi and welcome to the Chiari forum.
I have to ask the same question as the above poster....which surgery did you have......some Drs do a less invasive surgery to help prevent a CSF leak...but those surgeries can have very short lived benefits with the patient having to undergo a full decompression surgery.
Other possibilities are scar tissue, cerebral ptosis, and a related condition to Chiari that was not found b4 surgery....
Sometimes it can also be our activity levels....not sure why it comes back from activity but I know it can...or symptoms can flare...keep in mind surgery is done to restore CSF flow...and it is possible to have inflammation causing the same restriction of flow due to activities....or illness...colds, flu, allergies...etc...
I also agree with the above poster you will want to get in to see a true Chiari specialist....if you are comfortable with your original surgeon then call them....
Do keep us posted and know you are not alone to have symptoms return.
Was your surgery a decompression for chiari? I have read several accounts of chiari pain returning - in fact, symptoms can cycle and they can be affected by other conditions, and by certain activities. Sometimes I have read that weather conditions play a part in feeling symptoms. Do you have a trusted doctor? There is a list on this site that members have helped to create. It is a list of surgeons by geographical region who have helped others here in this community. Try to find someone you can start with in your area - but be aware that some people trave some to be with the right doctor. Good luck with your hunting and I hope you can get some relief for your symptoms.