I'm not sure who made the original "Biophone" radios...but I don't think it was Motorola.
Motorola did make the Apcor radio that was a different design then the Biophone (the Apcor was a white box while the Biophone...both the original model and the current one...was orange. I have some Emergency videos that have the original opening sequence that shows the original Biophone who I'll look at the tape and see who made the radio.
The reason the original radios were not very reliable was probably because the technology was new...making radios to transmit telemetry to a hospital.
The newer radios came with a keypad similer to a regular telephone for the medic to enter a code to contact the base hospital...something not used on Emergency...probably because there were not a lot of base hospitals at the time.