Every breed has it's place. All are useful in their own right. For myself I wouldn't buy anything other than an Arab for their toughness and versatility and beauty.
We have put down rubber mesh stabilizing matting in a gateway. What an improvement! Would recommend it however we did put some limestone chips under it to give the ground some help and it's just fine now.
I had a horse that did this sort of thing, exactly as you describe, really randomly. She was put down in the end and pm showed a brain tumour. Do be careful, and hope you get to the bottom of it all.
Keep riding, whatever you do, keep it up. It is very easy to get hopelessly stiff as you get older and then you won't feel balanced when you come to ride your youngsters. Even if you have maintained your confidence. I would buy the horse you are looking at (if sound) and just keep on trucking...
My youngster had liver problems last year. Milk thistle made no difference whatsoever to him. I had him on a sugar free diet. Thunderbrook, oat straw chop, soaked grass nuts and a few oats as well as good hay and pasture. Gradually the problem resolved itself. Why, is an eternal mystery to me...
We had budgies. The older lines did live a long time. We lost the last one at age 15. However I was told that newer show line birds are bred to grow big fast and therefore don't make old bones. We had a male and female and then 2 females. The girls fought like crazy and had to have...
I turn my boy out in a chifney. He is a pest otherwise. When I take it off I unbuckle the head strap and hold the bit so that he gently lets go. Maybe you could try this and give him a polo or something to get him to relax before you let him off so that he is more focussed on you rather than...
I'd give Turmeric a go as well. Gave it to our old polo pony who is 26 and very stiff in the morning and I can't believe the difference it has made in a very short time of administering it. Ours is a different horse on this.