Assuming you are seeing the Yellow Alarm on the BPTU card? Yellow Alarm is also known as an RAI or Remote Alarm Indication so while it is true the D-Channel would need to be set on the PRI card, that is not the problem. Something on the "far end" upstream from you is in a Red Alarm condition.

Where is the TBERD test taking place? Many times, I have run into the problem where the jack on the NID has become loose over the years and created these "phantoms". Sometimes simply giving the NID jack a good wiggle will clear the alarm temporarily and gives you ammunition to have the NID checked. The TBERD might work great because the technician is simply using the monitor jacks on the NID card. This will also mislead the SP because they see no errors on their circuit which is true from the POV of the NID before that jack.

If the tech is willing, they could also connect to your PRI card and make/receive test calls if the Toshiba side is set up correctly. It is possible the card is faulty but extremely unlikely. Toshiba hardware is solid. If you can find a BPTU on the cheap, you could exchange it to further build your confidence it is not your hardware. Any possibility a nearby tech could come by with an ISDN test set or a CommWatch T1 monitor and help you?

Another thing that could trip this up is framing and coding is not properly set somewhere. Generally, the standard is ESF/B8ZS, but if someone changed something to SF/AMI that could foul things up too. One horror story I had was having the SP take days to discover a repeater was set to SF/AMI between the site and the CO.

On the D-Channel, if this was working at some point where calls could be made/received on the Toshiba, the D-Channel must be set properly.

Final question, to your knowledege, has anyone adjusted programming on the Toshiba? Especially any clocking settings in system data?