Asterisk to NEC SV8100 E1 (PRI) issue?

Just throwing this out there in case someone has come across the issue.

We have a client who has an NEC SV8100 working on E1 without any issues.

We have implemented an Asterisk device with two E1 ports, with the purpose of migrating to Asterisk over a period of time. We cannot get calls from the Asterisk unit to he SV8100 nor from the SV8100 to Asterisk. Using the Asterisk device to call out via the same Carrier E1 and call in, no issues.

We have done this time and time again with no issues but not with a NEC SV8100. Yes we have the correct X-Over cables/ replaced them / confirmed correct CPE/Net config. We even took this unit to another system (with the same carrier - same E1 termination) and the system works with calls in and out.

We have done debugs, PRI Debugs (including comparisons) and the only part we are seeing is the following lines from an intense PRI debug (this is a call from our Asterisk device to the SV8100 E1)

T303 timed out. cref:32773
q931.c:5925 t303_expiry: Call 32773 enters state 0 (Null). Hold state: Idle
Fake clearing. cref:32773
q931.c:9219 pri_internal_clear: alive 1, hangupack 1
– Span 1: Channel 0/31 got hangup, cause 18

So really asking if anyone has done some work with the NEC SV8100 who may know the issue that we are facing.

Any thoughts would be appreciated…