texture streaming stops at 40%
but if click on the stop it does not stop
do u have a very high lightmaps mesh resolution in the scene? if yes try to reduce that
if not
here is a work around
save to a new map, start deleting assets like 20% of the assets then 40% and so on and with each bulk of assets removed try to build
once u figure out which mesh is causing this all what uneed to do is to delete and re add that mesh again and build the scene it will work normally