How much should a coupler move?

[RCSConstruction]

Still trying to chase down my grinding/vibration. Today I tore out the new gimbal and stuck an alignment bar in the coupler to see if I could tell if coupler was ripped/spun and it doesn't take any kind of force to move the coupler around. I can plainly see there is a misaligment with the coupler and gimbal housing hole.
With just one finger on the alignment bar I can push the coupler to align. (pushing sideways and up) If I put the alignment bar in and let it hang, the coupler moves a tad down. I thought these things were stiff?
Any other test to see if the coupler is messed up? I can't pull the motor for a while, was hoping not to.

Video-- ​https://youtu.be/nufqkQ2zuDA

 

[RCSConstruction]

[No message]

 

[alldodge]

Never tried that so cannot say with 100 percent accuracy, but that just does not look good. I would put a long rod or screw driver in there and have a bright light and see if I can move the center any. If it can be moved at all the coupler would need replacing, think it does anyway

 

[Bondo]

I thought these things were stiff?

Ayuh,.... It should be securely bolted to the flywheel,....

Sounds like ya found the problem,.... the bolts are loose or missin',....

 

[RCSConstruction]

Ayuh,.... It should be securely bolted to the flywheel,....

Sounds like ya found the problem,.... the bolts are loose or missin',....

Hey, Bondo! Always good to see you!
The coupler is bolted, it's just the rubber that seems to be soft? The center always springs back.
There is a ton of "play". I even stuck an old driveshaft yoke in and it wobbles a bit inside. Splines look good, but maybe wallowed out.. Heck I don't know.
At this point I guess I have no choice but to pull it and look it over.

 

[RCSConstruction]

Never tried that so cannot say with 100 percent accuracy, but that just does not look good. I would put a long rod or screw driver in there and have a bright light and see if I can move the center any. If it can be moved at all the coupler would need replacing, think it does anyway

I did try that. I swear it seems like I can move the center a tad before you see the rubber deform.
The prop spins fine is the weird part.

 

[Bondo]

Splines look good, but maybe wallowed out..

Ayuh,.... I thought you were sayin' the entire coupler could move,....

The splines should be Flat topped,... 'bout 3/32" wide,....