I usually have 400 geldings assigned to the BM. Mostly SD, but some AD as well. However, I have noticed when going through my barns, that some geldings are no longer assigned to the BM. I didn't unassign them, and they aren't schoolmasters, although it seems to happen with older geldings around level 6-9. Once a week I do Assign And Hire Riders > Reassign Horses > Consolidate Riders on the BM page, but that shouldn't affect the horses being enrolled with the BM. So am I doing something wrong, or is it a bug? Thanks in advance!

That tends to happen when the riders retire.

I see, thank you!

Why do riders retire before they hit level 10? I thought maybe it had to do with their age, but I didn't see that in the game guide

I have never seen a rider retire before level 10. I've had riders for months and never had to fire any retired that aren't 10. Do they level up to 10? For example, get a level 6 rider and just keep them forever until they hit level 10?

Riders will retired at roll over when they hit 65. In that case they just kinda dump all horses and vanish out of the rider lounge.

Riders retire the same week their experience is over 890. At least mine do.