Thanks for the explanation Neil, but to more precise describe my issue, I have 2 locations where i frequently experience this.

First location is the elevated highway Chonburi - Bangkok which I normally use. When I enter the highway the will locate me as taking ramp. As soon as I reach the toll booth it will start recalculating and place me again on the road below. When I reach the next access point, while being on the highway already, the GPS will again tell me that I'm taking the ramp, then recalculate and say I'm on below road.The issue finish at the 4th access.

The second location is from Rangsit direction Don Muang, where i seldom take the Don Muang highway, but where the Zumo tells me that I'm on the Highway. I think overthere the issue stops appearing when I pass the airport.