This is likely to be caused by the bridge not being explicitly marked as suitable for walking on the OpenStreetMap database. You would need to temporarily turn off the Auto-Plot switch to plot across the bridge. Or you can update OpenStreetMap to tag a path as suitable for walking, as OpenStreetMap is a community project.
I've just started to plot a route near Youlgrave/Over Haddon (Derbyshire Dales). The path goes over a river where I know there is a small bridge but the route won't track over the bridge thereby adding an unnecessary extra mile to the intended route. Is it because the map 'thinks' there's not a bridge or.......?
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