Using a handful of mods (Skyve profile JSON available on request) and I've drawn a perfectly straight and level network of REV0's "HST Track" across my map. I then tried to connect the ends of the HST network (on both sides) to the edges of the map. I have fog turned off and I get no arrows (or trains).

Skyve reports no compatibility problems, but here's a quick list of some mods I'm using that might be interacting:

81 Tiles 2
Catenary Replacer Updated (I noticed this doesn't work with the HST tracks)
Game Anarchy
Line Tool
Network Anarchy
Network Multitool
Network Skins
Node Controller Renewal
TMPE
Transfer Manager CE

Any help would be greatly appreciated!