Have done a wander around house with radio, amd found that near to my answerphone base unit there's a substantial pulsating "puuurrrup". The base unit, being in the hall, is distant from the router. The slave is quite near the router, 6", but seems OK.
The DECT units, Panasonic, are about 8 y.o. At that age are they likely to have deteriorated appreciably?