I have a Shiva/Kinetics Etherport SE in my SE FDHD!

Mine does not have a 10BASE-T connector on the daughterboard, but it does have an AUI connector with a CentreCOM 210TS 10BASE-T transceiver.

10BASE-T was well, well before my time in the networking space, but my understanding (and according to Wikipedia) is that 10BASE-T can run in either half-duplex or full-duplex mode. I'm not sure of the specifics, but it does seem like some newer devices don't support half-duplex (one side can talk at a time, think Walkie Talkies) mode. That might be what is going on with your AirPort Extreme.
For the record, my CentreCOM 10BASE-T transceiver and my Dayna SCSI/Link-T both talk happily with my Ubiquiti UniFi In-Hall HD AC (2 years old), as well as my Cisco SG300-P (4-8 years old).

Mine does not have a 10BASE-T connector on the daughterboard, but it does have an AUI connector with a CentreCOM 210TS 10BASE-T transceiver.

10BASE-T was well, well before my time in the networking space, but my understanding (and according to Wikipedia) is that 10BASE-T can run in either half-duplex or full-duplex mode. I'm not sure of the specifics, but it does seem like some newer devices don't support half-duplex (one side can talk at a time, think Walkie Talkies) mode. That might be what is going on with your AirPort Extreme.
For the record, my CentreCOM 10BASE-T transceiver and my Dayna SCSI/Link-T both talk happily with my Ubiquiti UniFi In-Hall HD AC (2 years old), as well as my Cisco SG300-P (4-8 years old).

