NX Unable to edit sketch dimension back to its original value with error.

"The dimension could not be edited as requested. Try relaxing dimensions and/or relations".

The sketch solver finds relations from the position of the curves. Connectivity relations (such as Coincident and Point on Curve) are stronger than other relations - the intent is to keep a profile connected. In a situation where two curves need to move separately and sometimes touch, the found connectivity can cause a sketch to lock up. There are several solutions that can be used to inform the solver that two curves are not supposed to be connected. These solutions have been introduced in various releases from NX 2007 through NX 2306. 

1) Reference Geometry - If one curve is active and the other is reference, the solver will not lock them together. Instead it will find the coincident relation between them and allow that relation to be relaxed by the solver or by the user.

2) Group membership - If two curves of the same type (e.g. both active) need to touch and separate, putting them in separate groups tells the solver that these are not part of the same profile. Coincident relations are still found, but can be relaxed by the solver or by the user.

3) Ignore Relation - The found Coincident relations can be marked as ignored so they will not be found ever again. Any one of these three solutions addresses this problem by providing the additional information to the solver so that it doesn't connect the two lines and lock up the sketch.

PR10206682