When using Space Age Hard Mode Mod Pack I'm getting the below error when loading factorio:
3.570 Error ModManager.cpp:1767: Error while loading entity prototype "lighted-electric-transmission-tower" (electric-pole): Layers of rotated sprite need to have equal direction_count.

At ROOT.electric-pole.lighted-electric-transmission-tower.pictures.layers[3]
Modifications: Lighted Electric Poles + › Hard Nauvis

https://mods.factorio.com/mod/Space-Age-Hardcore-Mode?from=search

That's... really odd. The Electric Transmission Tower doesn't have a rotated sprite. It doesn't rotate. The "lighted-electric-transmission-tower" is not my prototype - mine's just "electric-transmission-tower". So either this is someone else's prototype, or Space Age Hard Mode tries to create copies of prototypes and is setting the Tower to a rotated sprite - which it doesn't have. I'll have a look at the Hard Mode mod and see if I can identify a point of conflict, but this doesn't seem like something I can fix on my end. Will keep you posted.

edit
I'm pretty sure it's Lighted Electric Poles doing this. I've only had a cursory glance since I'm off to lunch presently, but:

local pole = data.raw["electric-pole"][item.place_result]
local newPole = flib.copy_prototype(pole, newName, true)
newPole.icons = flib.create_icons(pole, lep_icons_layer) or lep_icons_layer

Seems like either flib is trying to create a rotatable sprite, or else is failing and the tower gets just one icon. I'll investigate as time permits. Could be something on my end that's tripping flib, I'm not sure.

Actually, I was incorrect. This is not an issue with Electric Transmission Tower at all. It's an interaction between https://mods.factorio.com/mod/Lighted-Poles-Plus, Hadcore Nauvis and No Rotation for Electric Poles. Any combination of the two seems to work fine, but the three together start causing crashes. I don't know what the issue is, but this smells like load order to me. I would suggest bringing this to either the Hard Nauvis or Lighted Poles mods discussions. Feel free to CC this discussion if you'd like.

I'll have a root around the mods a little bit to see if I can give you a more concrete answer, but I make no promises. edit Yup, it's Hard Nauvis. That mod has a deliberate override for Lighted Electric Poles which adds extra layers to the entity's pictures for reasons I don't quite follow. That then causes issues with electric poles which don't rotate, as those only have one layer. At least I think so. This is something that Hard Nauvis needs to account for, as its override is what's introducing the crashing issue.