Sounds like your i2c cables may not be oriented properly. Ensure that your ground wire is accurate. Here is an excerpt from the quick start guide (pages 3-4):
On the Teletype and Trilogy Modules, the II pins are oriented top to bottom (ground on the top).
On the TELEX modules and Ansible, these pins are oriented bottom to top (ground on the bottom).
On the TELEX modules, two vertical columns of II pins are present and slightly separated (2x3 connectors won’t cover both columns – they are designed for jumpers).
Ensure that you are appropriately orienting your ground wire when connecting the devices together. The rule is “Twist to the Teletype or Trilogy” - if you need a mnemonic.
Let us know if that solves your problem.