STEP 1
I. Matrix doesn't seat passively
a) Internal lingual ledge of matrix is binding on cingulum(s): Reduce its bulk (use laboratory bur)
b) Incisor(s) are rotated, binding on internal labial or lingual walls: Relieve internals
c) Internal lingual ledge is pressing on incisal papilla:  Reduce accordingly.
II. Mandibular midline doesn't contact on the Discluding Element (DE).
a) Reposition matrix (as far to the right or left as necessay) to ensure the mandibular midline (24/25) is positioned under the DE in closure.  Ignore the maxillary mid-line.  Afferent signals from the right and left mandibular nerve must be as equal as possible. (go to Step 2, III )

STEP 2
I. Flaring of maxillary incisors doesn't allow for the DE to be parallel to the maxillary occlusal plane.
a) Ruduce the internal lingual ledge significantly and rotate the matrix to improve  desired orientation.
1.  Reduce the vertical dimension at the distal end of the DE (grinding away the "heel"), and possibly add acrylic to the anterior end, thereby "rotating" the DE's occlusal plane.
II.  In either full retrusive or protrusive, the lower incisors can either "get behind" or "get in front" of the DE.
a)  Add acrylic to either extend the DE distally or anteriorly, to ensure the lower incisors contact the DE perpendicular to their long axis.
III. One of the centrals is "taller" than the other, making simultaneous contact in centric closure not possible. When only one central contacts, the mandible will reflexively attempt to find equilabration, that is,equal imput from both mandibular nerves. Upon immediate contact with one central, the patient will either report an "uneven-ness", or their jaw will immediately shift so as to contact the other central (an excursive movement).
 a) The preferable remedy is to reduce the incisal edge of the taller tooth.
1.  Once the patient is aware of the discrempancy, they will usually volunteer to have the taller tooth reduced.  (They have typically been aware of the uneveness for years, and my see this as an esthetic benefit)
 b) Contour the DE by angling it laterally so as to simultaneously contact both centrals. This method is contra-indicated when incisal edge discrempancies are significant, due to the creation of potential resistance to lateral movement.

STEP 3
I. Hairline fractures appear within matrix, or matrix cracks apart.
a)  Direct application of the liquid monomer to the matrix will allow it to break apart, while a too thin of an acrylic mixture allows for the hairline fractures.  Do not "condition" the matrix with monomer.  When combinding acrylic powder to the monomer, add powder until it no longer is absorbed the monomer.  Let set until it is quite sluggish before loading it into the matrix.

STEP 4
I.  Patient reports that the appliance feels tight, or feels as though the appliance is applying pressure to their teeth.
a)  Assuming that the matrix fit passively over the incisors prior to reline, there is some degree of distortion of the reline acrylic internally, or "crumbs" or acrylic need to be cleaned out.  If after a couple of attempts of relieving the internal lining and the patient continues to report tightness or pressure, grind out enough internal acrylic so that the matrix again fits passively. Repeat fabrication step 3.

Go to regarding "loosening" of the matrix after use.

STEP 5
I.  Although posterior teeth are discluded in a centric position, there is posterior occluding in an excursive position. (Typically, a palatal cusp will occlude with a distal-buccal-or-lingual mandibular cusp)
a)  There are two choices.  Either increase the verticle dimension by adding a layer of enough acrylic to the occlusal surface of the DE to provide disclusion, or the preferable method of reducing the the cusp tips of the occluding teeth (this is an obvious demonstration of significant occlusal interferences).
II. The tips of the canine teeth can occlude with each other in an excursive position (when the nighttime NTIcss in place)
b)  Same as above.  However, if the canine cusp tips show no evidence of any occlusal wear, no modifycation be even be necessary.  Canine cusp tip wear (or the lack of it) is the evidence of excursive canine clenching (or absense of it).