I'm using the last non-beta. My experience is, too often v4 vector map does not load. At all, or sometimes a bit. Sometimes load after map drag. Seen that especially in route planner. Sometimes Locus cache has to be cleared.
It is annoying if Locus insists on looking like in screenshot.
I think it loves to do this when the map is moved to more far away locations.
Edit: now cache delete, restart whole phone, no matter if v3 or v4 map(only v4, oam Germany North vs. Germany mid), no matter which theme, mostly no map buildup, sometimes at zl 13,but not above. no more idea except using Osmand. Want to not risk uninstall Locus.