I suggest:
(1) Bring the mechanic (preferably one who specializes in suspension, etc.) and drive to that place where you experience the problem. Then once the problem occurs, call the attention of the mechanic, "e.g. AYUN! Randam mo ba?"
(2) Now, swap kayo ng makaniko. Let him drive while you sit at the passenger side. And ask him to go drive through the same area.

Kung competent yung mekaniko, I'm sure hindi ka na aabot sa step (2). Mararandamam na niya yun and he'll have a good guess where teh probelm is.