The route that I sent debug logs for per post https://world.waze.com/forum/posting.php?mode=reply&f=3&t=27526#pr318416
was roughly this Livemap route
If multiple routes are shown, It's the one via N1 South, M12 West. From what I gather, it's not specific tiles that does not load. The constant recalculation of the route seems to be the bigger problem and that could possibly interfere with tile loading. It certainly does interfere with navigation instructions.
The same route on an Android tablet for the same drive was rock solid with no missing tiles or any route recalcs.
If I can assist in setting up a controlled test for a specific short route in the area, please let me know.
I normally use Android, but I'm sure I can persuade my son to do something else for a few minutes while I borrow his phone.