For the life of me, I can't set up call forward (all calls) to a certain destination from a station on a 2400ICS. The system is old, and never had problem setting up Call Forward All call. I can set it to another station, or to an external number. No problem.

This time around, I want to forward to a phone that's on an SV9500, and the 2 systems are connected via CCIS. Even this is working for other cases.

I can set this up with a destination being the SV9500 to certain set of stations, but the needed destination I can't enter.
From ICS 2400 from station 5000, I can set call forward with *1+dest.
So Ext 5000 dials *1 555437 and it works (and 555437 is an extension on the SV9500)
But from ext 5000, dialing *1 645444 fails (even if 645444 is another valid station on the SV9500, and can be dialed just fine from the ICS). I enter the digits slowly, and I get as far as *165644. At this point I get RST on the phone. So something dial-plan related I assume

On the 2400 ICS, I have AASP for ACC 64544 (I only define the first 5 digits), CI=N/H/B, SRV=LCR, RT=31.
The AFRS is also properly set with TN=1, RT=31, FLG=1, NPC=6454 (I only define 4 digits here), and OPR 58 (which sends the call to the CCIS route).
AMND is set TN=1, DC=6454. MDN=6 (as all 6454 numbers refer to 6-digit extensions across the CCIS).

This is the same setup method as the other, working extension on the SV9500 can be forwarded to.

Again, in a nutshell, I can set call forward all calls to some numbers, and can't to some other numbers. And I can't find where is the problem in programming.

I'm not sure what other command to look at. Any ideas?