What you can try is to remove all blades, remove servo arm from the tail servo (or just ball linkage) so that you can move with push rod by hand.
Then spin up the heli to approx. your flying rpm.
Then carefully move with the push rod by hand and check how smooth it is working along the travel. This could help you a lot with determining if the mechanics is perfect also when running. In some cases it could cause a big difference. Then pilot can find that for example axial bearings were not in a proper direction or something is not fitting well, yet normally all is looking very smooth. Basically if this will work smooth, then you can say that the mechanics is really good.

If you have measured vibrations with Spectrum Analysis in the software, then it should be all good. But if you have a plot then I can confirm it.

I have completely forgot about static discharges - this could be also reason for this random jittering. Basically on any axis. Check if the belt is not loose in the boom.

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Spirit System developer

Hi again,

I did like you asked and the mechanics are definitely good and smooth.
I have attached the vibration analysis for tail blades on, you can see a little spike which I have been unable to reduce any further through balancing, otherwise the spike is completely gone with tail blades off.
The tail belt is a good tension and lubed with silicon spray.
I did take the tail completely apart last night and rechecked nothing is bent, the bearings are good and the mechanics are smooth.
I have put on a new set of different tail blades and haven't had a chance to re-fly it yet so I'll see how I get on.

This plot looks very good. If it looks like similarly on all 3 axes, then it is definitively pretty OK.

I have just noted that you are probably using some older firmware/software version. Maybe newer version could improve it, although I dont know about any particular change that should affect this behavior. But you can leave it as one option to try that is worth also for other reasons.

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Spirit System developer

After a wait I now have a new tail servo installed and the Spirit firmware updated.
I don’t know if it is because I’m now using a full sized tail servo rather than a mini or the software update but the issue seems to be resolved