Horse would not settle.
Horse would not settle.
Horse would not settle.
Horse would not settle.
Horse would not settle.
Horse would not settle.

Ad infinitum.
Every horse. Every race.
Pacifiers have no effect whatsoever.
First season never had a single problem with temperament. In the second season, the same horses have become unmanageable.

Am I doing something wrong?

No try Gelding it if a colt.

I have this problem with my jumps game and for the horses which have potential slightly lower than maximum it can be a nightmare.

My problem is I'm still in the relatively early days of the save (around 15 years in) so i cant afford to be too fussy with who i put in my breeding barn. I'm just hoping over time the quirks iron out as i put in fresh supplies to my breeding lines.

Howdy

Do they all have the "excitable" temperament?
I have not had this on ALL my horses in one season.

Have you tried....

Might need something stronger than Valium.

I would geld them but they are all Group class.
The 4yo won The St Leger and The Derby in the first season.
The 6yo won a G2 and a G3 over 8f and 10f.
The 5yo is a G3 over 14.
Last season (my first) they had no temperament problems at all. The stayer had a blue triangle in a couple of races.
Now every horse in every race refuses to settle.

I introduced a couple of mares to the yard (otherwise all male) to see if that made a difference. It didn't.
Do the males all become more temperamental as they get older?

Some horses can’t jump others are just pants. Shoot it, sell it etc and move on.

More serious response, yes quirks can develop as they age if it is in their bloodline, you can with effort breed it out. One of my best league level g1 chase lines came from a quirky horse who was also a g1 flat 3yo before switching to fences at 5yo. So ok to breed with mares with no quirks bin any offspring who inherit the trait, rinse and repeat. Also note some horses are at there best when 2yo or 3yo and will only go downhill from there no matter what you do, they tend to breed like horses in my experience, but being able to win G1 classics is no bad thing, you will find other horses and lines will develop later for the older races and give you more overall coverage. But don’t be afraid to cut your loses and change direction only so far you can flog a dead horse