I would get with your PEBLO to see if you can get some support. You are supposed to remain available for MEB/PEB actions. See AR 635-40, Appendix E, "E–4. Administrative control of Soldiers before final PEB action
a. Soldiers processed as outpatients will remain available to the MTF commander or president of the PEB until the
PEB completes action in his or her case.
b. Soldiers processed by MTFs in attached status will normally be retained at the MTF until PEB processing is
completed. The Soldier may, however, be authorized to reside elsewhere pending completion of PEB action.
c. Soldiers processed by MTFs in assigned status normally will remain at the MTF until PEB action is completed.
The Soldier may, however, be authorized to reside elsewhere pending completion of PEB action."
Seems to me that if you are at NTC, you would not be available as required. A separate issue is if you should be performing duty at NTC as it may be outside of your profile (I don't know what your limitations are, but the point is, there are two issues- your availability to act on your case and your medical status/ability to actually perform this rotation at NTC). For the latter, you may check with your doctor (maybe-your brigade surgeon, but I am not sure how sympathetic he may be and you may want someone outside of your chain looking at the issue as they may be more objective).