I read in a magazine back in the day that the person who built the Kamelion prop had sadly died in an accident. It was a very complex mechanism for it's time. (Like a Disney audio animatronic figure.) Nobody else knew how to work it properly, and the prop frequently malfunctioned. All of this contributed to Kamelion's short time as the Doctor's second robot companion.
Maybe the new series will resurrect him someday?