Ok, so there are a few options here.
1) The RJ48X dongle plugged into the smartjack is fubar'd and shorting out/frayed/etc. If it's plugged in unplug it and directly connect the smartjack to the T1 port. For some reason they like to get corroded and screwed up. Probably all our lovely humidity and salty air.
2) Whatever cables/connectors running between your T1 port and the smartjack is junk. If you have inline couplers, handmade cables, or other such error-prone things then replace it.
3) The T1 port on the PBX is loose/smashed/broken. Get on the phone, then walk over to the PBX and start wiggling the connector. If the calls drop with moderate agitation, then there's your problem.
4) Last is a failed hardware card. If it's an older switchvox then this is where my money is. I've been down this road before with Digium cards and they were notorious for this in their earlier production runs.
So, I'm putting my money on option #4. Given the fact that the card reports red then instantly goes green is a somewhat tell-tale sign of this kind of failure. Problems 1 and 2 usually result in an obscene about of bit errors/etc. We would be talking 6-digit error figures in a 24-hour period or more (depending on the bit error). Problem 3 is easy enough to prove with a little investigation.
Unfortunately you don't have a Sangoma card so you cant get to the real CSU/DSU error stats. If you did you could actually look up and see exactly what KIND or errors you were getting other then just "errors".
