Our uSR measurements on superconducting Y1-xErxNi2B2C shows a slowing of the Er spin dynamics upon cooling to 2.5 K, but the depolarisation rate does not critically diverge and the asymmetry shows no sign of a spin glass transition. Arrhenius behaviour is observed above ~0.2Tc, between 30mK and 0.2Tc, the depolarisation rate is temperature independent, indicative of quantum tunnelling, possibly of the Er spins themselves or an alternative magnetic ground state. Therefore, we propose to use the HiFi spectrometer to investigate the magnetic nature of the low temperature plateau.