Pimples at Layer Start/Stop?

I printed a Part with Prusament PETG (matte black). All in all it looks great for me. But there are pimples at the inner perimeters. Looks like it is the start and stop point of the nozzle for each layer? Anybody an idea how to hide/improve it? PETG 240°C Pressure advance 0.05 Extrusion factor 0.94