Sorry, I do not have a good solution now. Workaround is just to wait and then save the map as it starts. New saves will load quickly.
#Several minutes loading by The Netherland from workshop
pseudo turtle
It is the new more precise topology search algorithm that tries s to reach the other stations by drawing the connector to them. It is quite fast when the map contains walls that enclose the stations in enclaves so that the area you can reach from each station without crossing other station is reasonably small.
If the stations are not properly enclosed, it not only causes long search but also wrong input for the contract generator. If you can bypass a 10km autoblock by a 1km track, topology search finds this shortcut and gives much less money for the contract. Or makes ridiculous one-time contract schedule.
So the long duration is a symptom of a deeper problem in the map.
trail dust