[Tannaton]

I've seen this before on a XC60. The TPMS system is a rotational one so uses the ABS sensors, hence if the ABS system have a problem, the TPMS system comes out in sympathy.

Whilst I don't think based on what you said the car is inherently unsafe, I'd keep driving it to a minimum - provided there is no red light on the dash or "stop safely" message.

As will all these situations - get the codes read on Volvo gear. Likely to be a £50 wheel sensor.