When i plan a route manual along low altitude route segments then most of the time it go’s well. But when i let the MSFS route planner do it for me i get the strangest altitude changes from ATC.
I use Navdata Airac 2101 beta for MSFS and also on simbrief and Little Nav Map.
I plan my route in one of the two route planners and past the route data manual into the sim.