Ok had a quick look at the route after transfer and can see at least 1 problem and thats between llwyn-y-gog and Aberhosan, whats the cause of this i can not tell and it may not even occur on your device when transfered but it may be there. picture below, and as i have said i have no clue as to why this would occur on my devices, it may be just some sort of anomally in that part of the map.