Is it the idea to first bend the rim to straighten it as best possible before trueing it?
The reason I ask is that today a spoke snapped during my commute and the wheel whobbled badly after that. I had this wheel trued some months ago, it was buckled badly before, and it seems to me the LBS only played with spoke tension to fix it. Some spokes seemed loose, others very tight when I got it back, but since it was true I didn't worry and I don't have any trueing know-how.
You probably need a new rim. When a wheel "buckles," the rim can be permanently bent. The only way to get it straight is to over-tighten some spokes to pull the rim into true. That sounds like the case with this wheel. Get the rim replaced or buy a new wheel.