2017 TC125 Rear Shock

It’s common. What I felt worked the best was the pro circuit linkage and knuckle. The link by itself helped, but not as much as the whole setup. The Luxon setup would be my go to if I was buying new, I just happened to luck out on someone selling a used one cheap. 

The stock KTM linkage is a "low leverage" setup.. or something like that.  Notice that KTM's run much lighter shock springs, relatively, than all the Japanese bikes.   Where most Japanese full size bikes are in the 5.3-5.7kg range, KTM's are 4.2 - 4.5-ish.

Most of these aftermarket linkages basically turn it into more of a traditional Japanese bike setup and to get the full benefit you need a revalve and a new shock spring.  Mr. Luxon can explain much better but that's the general gist of it.

https://motocrossactionmag.com/mxa-team-tested-pro-circuit-ktm-rising-r…

I never had a complaint with how the shock/rear end worked on my 2016 125SX, but my pull arm blew a hole in it so I got a good deal on a used Ride Engineering pull rod and it made the bike handle even better, so I could imagine a full Linkage with the correct spring rate and valving would be magic. I would highly suggest trying Powerband suspension who’s now located in FL, they did a lot of orange brigade KTM 125s and 250s during that time period. 

It will never work like a 4 stroke rear end , my yz doesn't either 

Also a +1 for Powerband. That who I send my stuff too and have for a years now. They also do reeds kids stuff. 

Thats not accurate on the KTM’s unless you are specifically referring to the engine braking which problem isn’t what he’s talking about. 

No a 4 stroke will put the power done much better than a 2 stroke,the power pulse on the 2 stroke ( twice as often ) always breaks the rear loose easier and it never is as planted , also the light weight of the 125 works against it for traction compared to a 4 stroke 

That's why people love the 4 strokes ,better traction and more predictable

You will chase this forever 

I'm going to assume you've carefully tested with the High speed compression adjuster on the shock, but I don't see it mentioned.  The HSC is much more sensitive on the Austrian bikes than the Japanese bikes.   1/4 turn can be the difference between plush on accel chop or refusing to move.  It's a fine balance between getting the plushness you want while still maintaining enough anti-squat and chassis balance for cornering.

Also if it’s too soft on the high speed it will swap towards the end of the whoops as it packs up. 

On my '17 TC250, I had a similar issue originally.  When I would dial in LSC and HSC enough to be good over most of the track, it would be too harsh in certain sections (particularly on acceleration bumps).  If you soften compression to make it more comfortable there and in other rough sections, then it's too soft overall everywhere else.  Pretty typical motocross suspension dilemma, but the stock shock was more problematic for me than on other bikes.  One other note, the front to rear balance is pretty important on these bikes and the early AER forks rode higher and blew through more than later ones (or revalved ones).

The aftermarket linkages are all a little different, but all primarily affect the later parts of the shock travel.  Many threads on here about that: https://www.vitalmx.com/forums/Tech-Help-Race-Shop,42/Factory-Connectio…; Would be surprised if you're using that much travel on acceleration bumps. (edit: another link about linkages: https://www.vitalmx.com/forums/tech-helprace-shop/best-ktm-linkage)

A revalve that's matched to whatever linkage you have will be better than stock.  Had mine revalved by Enzo (TX location) and it was good enough that I never considered different linkages again.  A revalve by Enzo or REP would likely fix those issues without any problem.  

Sounds like a linkage or shock bearing may have seized causing the bind that bent the shaft.

I had a shaft eyelet end snap off on my 1985 500CR husky and I think that may have been the reason why.