Forge 47.1.39
Horses 1.20.1-11.4
latest logs: https://pastebin.com/uprVcXhb
At startup there is an issue with one of the recipes on line 73
[20Jul2023 10:34:05.853] [main/ERROR] [net.minecraft.world.item.crafting.RecipeManager/]: Parsing error loading recipe horse_colors:netherite_horse_armor_smithing
com.google.gson.JsonSyntaxException: Invalid or unsupported recipe type 'minecraft:smithing'
Then as I'm in the game moving around, periodically the server threw exceptions when trying to generate the horses. Currently, mod is not working at all in 1.20.1 so I had to remove it.

Fixed by b510f46. Thank you for the detailed report.

any eta on when you'll post the update with this fix?

Here: https://www.curseforge.com/minecraft/mc-mods/realistic-horse-genetics/files/4657479

thanks, was waiting for another entry there. I see you replaced the 11.4 with 11.5 instead. Didn't think of checking that. :-)

Yeah, I took down the other because that was just such an awful bug. Hope you have fun!