When using a spline IK the armature that is not hooked to the curve has a strange delay that distorts the mesh. In pose and object mode when moving the root the armature will break apart so that one portion lags behind and stretches. This gives the mesh a rubber like effect and that information is stored in any animation.
The spine and tail are hooked up to a curve which are controlled by separate armatures. When I move the root the spine moves as expected, but the pelvis stays behind and the tail curve warps. 
you may have to post us a file to see what is going on…
if you can’t do that yet in the BA forums goto…
note that they have a special .blender file upload … (find in the upper Right of the website…
once posted… come back here and give us your upload site…
So you say your using two Armatures?
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Thank you @norvman and @Hadriscus for your replies. Looking into the depsgraph was really informative. Unfortunately I can’t post my file anywhere, but I did find the solution!
I have an armature that is hooked to the curve on the tail as well as the main armature that takes care of all the model deformations. What I had failed to do was parent the armature. I parented the curve controlling armature to the root of the main armature and everything is working as expected now.
Very cool… glad you got it fixed… please mark as ‘solved’