Servo Wiring and Tuning detailed How To example Mesa 7i77.

I think you would be better off with a new config if the feedback is detached somewhere.
Yes that is the vibration i am refering to, try to reduce that by also setting the deadband, it helps minimise the vibration when stationary.
Do not try to tune anything until you get to the point where you can see the DRO in Linuxcnc change when you move the motors by hand, then check if they are counting in the right direction, then you can try to enable the drives and check if you need to reverse the output.
The main thing is when you enable the drives in Linuxcnc they should stay put, try to jog them very slowly after setting the jog speed to a reasonable value (50 - 100mm/m) and see if they stop ( some drift is ok at this point or hunting ).
Only after checking all that proced to tune the P value till you get some vibration while stationary and some more vibration after jog and stop, then lower that value till you get barely noticeable vibration, tune the deadband, test, see if you can increase P by just a bit and still have barely noticeable vibrations. Now try to move the motors by hand while enabled, they should fight back quite vigorously the more you try to move them.
Now the tuning can start.
If you notice that the motors can move a lot before they fight back, deadband should be adjusted some more.
Now you can try ading some I or/and D till you get very stiff motors that fight back as soon as you try to move them. It is much better to have I and D set to zero than to have them at wrong values, this can be tuned even after everything else.
To tune the FF1 there are two methods, the one i use and explained here, and the other that PCW recommends by setting the output scale to maximum velocity in machine units so the FF1 is always 1 ( please do check this as i might have missed something as i never used this method ).
If using the method described here, start with 0.1, then 0.2 and so on all this while the velocity is set to 50-100mm/m, check the feedback for the least error while jogging, then add another decimal like 0.25 and test again for the lowest error, then do 0.255 and check, then 0.2555 and so on till you get a flat feedback line. Increase the jog speed a bit and test again, add decimals, increase speed, and so on. Those values are just example, but do not worry if you end up with something like 0.345678.

@Type 0
You are better of by doing a new config than chasing gremlins at this stage.
You can post the config files here, you might have already but am on the phone so not much use for now from me.
I'll have a look when i get my hands on one of my laptops.
Regards,
Tom.

@Huey
Thank you, i missed answering that.