QSIG between Definity G3r and Mitel 3300 - MWI problems on only certain links

[Lundah]

I have a cluster of Mitel 3300's (release 9.0.3.34) with several QSIG T1 links over to an Avaya Definity G3r. On some of the links, I cannot pass MWI from the centralized VM in the Mitel cloud over to the Avaya to light the lights on the Avaya users' sets. On the Mitel end, the non-working QSIG links all require the Termination Mode setting in Link Descriptor to be LT. Any link set for NT works fine. On the Avaya side, the links requiring LT all terminate on 120A2 CSU's on the T1 card, the working links terminate to either 120A1's or 356A's. Trying to figure out what's unique about the links on the 120A2's that's causing my MWI requests to fail.

CCS trace from Mitel - successful MWI change:

14:06:22 VO1223 DPN 2A ISRM_I  ;10;*1#*50*33000#*100*VMHunt#*19*I#*58*CO*B#     
14:06:22 VO1223 DPN 2C SSRM_C  *58*CW*Ud@@@@@@@w];7E;T`#*171B#*58*CS*01#35014   
14:06:22 VI1223 DPN 2  CRM/CIM ;14;

CCS trace from Mitel - unsuccessful MWI change:

14:23:21 VO1246 DPN 2A ISRM_I  ;10;*1#*50*33000#*100*VMHunt#*19*I#*58*CO*B#     
14:23:21 VO1246 DPN 22 SSRM_C  *58*CW*Ud@@@@@@@w_My@#*172B#35014                
14:23:21 VI1246 DPN B  CRM/CIM ;4;*58*CP*G#

The hex value in the CRM/CIM message is key, one link returns code 14, which is successful, while the other returns 4, which is defined in the BTNR 1888 standard as "Subscriber Incompatible". But I can't for the life of me figure out what's unique about the 120A2 integrated CSU on the Avaya, or how to fix it.