I too would like to report the same experience. I've been horse training since 2016 and this is downright depressing.
I have never ONLY popped 9 skills on a T8. The lack of skills obtained during leveling is shocking. I have been imperial trading my T8s to at least get the flower of oblivion.

Yes, this bug messed up my T10 peggy, now I need to reset it to make it learn all skills, this is depressing :<

My latest t10 hasn't learned a skill since level 11 (its currently 17). I thought it was just really dumb since my other T10s didn't stop learning skills until low 20s... This makes a lot more sense.

I have 5 t8 horses and they learn only 8 or 9 skills at level 25, please fix it.

Well I don't know how much it's related to this bug, but there could be another bug with t9 horse awakening.

Did yesterday a full seasion of 50 trys on it an nada, and today another 10.

It fees like it might be bugged as well, like what are the chances to fail so much.

T8 at lvl 28 only has 5 skills, this is not the norm

Yeah this is really frustrating :/ Since returning to bdo most of my breeding has given me the newer T8s they've made that I don't even like. In the past few weeks I've finally obtained some of the original T8s that I actually like, only to find that because of this bug all of them turned into total duds. Lovely. Considering my VP expired today and now this bug means I can't level horses, sounds like a good time to take a break from bdo until this is resolved. I'll prob log in on april 9th for my bday and do one t10 attempt and then quit logging in until I hear this bug got fixed. That or just afk fish or something until its resolved.

Hopefully word can be spread about this and quickly so more people don't get screwed over. Considering the direct connection between horses and real money via skill changes, this can be quite the serious bug and more people need to be made aware X.X

I got a T9 that I lvled to 30 to try for Mythical, and wow never had such a bad T9 at 30 before, same with the Mythical that I got, even reset growth once but still, the ammount of skills learned was horrible. Found out its a bug way too late, hope we get another mount growth reset as compensation

the skill are not working properly t9 dine didnt gain any skill for 13 consecutive level have to use horse skill change, but the rng is ass, as of now that dine is trash,also multi t8 lv30 with less than 9 skill or even 5 to 6 skill 

I, too, am holding off on levelling for now until we get more info on tihis.  Skill learning has been bad - initialy I figured it was just a string of bad rng.  But adding in the less than normal rng on T9 awakening (my RNG there has always been good compared to RNG anywhere else in the game! XD ) and there seems to indeed be some underlying issues.  Keep us posted on this, please - until then, horse levelling for higher tier mounts is on hold.