Ultimaker Cura is not always retracting in exported G-Code
It's likely that you're hitting Cura's Maximum Retraction Count (retraction_count_max) within the Minimum Extrusion Distance Window (retraction_extrusion_window). This is a misfeature supposedly designed to avoid grinding/flattening the filament, but of course acting on it will ruin your print in exactly the same way you're seeing. I think setting the window to 0 or the maximum count to some ridiculously high number like 1000000 will fix the problem.
Note that it's exacerbated by the thin nozzle making the number of retractions needed take place over a much smaller extruder-axis move distance than what you'd have with a normal 0.4 mm nozzle. This is probably why nobody has noticed and complained about the badness of Cura's defaults here.