I can confirm that the physical construction, as shown in your latest image (Lower face-plate 2.PNG), corresponds with the printed circuit wiring as shown in the earlier image (Lower face-plate.jpg).
Well B*CAT with the lower front-plate removed i inserted the plug from telephone cable direct into the SSFP and made a call to my landline number the CRC/errored seconds showed up.
Project History
1. phone cable disconnected from lower front-plate = errored seconds when phone rings
2. lower front-plate removed & phone cable disconnected = no errored seconds when phone rings
3. lower front-plate removed & phone cable connected to SSFP = errored seconds
to me it looks like an SSFP issue rather than the lower front-plate i just don't know any thought's are very welcome.