  In 2017, the Be/X-ray transient 4U 0115+63 exhibited a new type-II outburst
that was two times fainter than its 2015 giant outburst (in the Swift/BAT count
rates). Despite this difference between the two bright events, the source
displayed similar X-ray behaviour after these periods. Once the outbursts
ceased, the source did not transit towards quiescence directly, but was
detected about a factor of 10 above its known quiescent level. It eventually
decayed back to quiescence over time scales of months. In this paper we present
the results of our Swift monitoring campaign, and an XMM-Newton observation of
4U 0115+63 during the decay of the 2017 type-II outburst, and its subsequent
low-luminosity behaviour. We discuss the possible origin of the decaying source
emission at this low-level luminosity, which has now been shown as a recurrent
phenomenon, in the framework of the two proposed scenarios to explain this
faint state: cooling from an accretion-heated neutron-star crust or continuous
low-level accretion. In addition, we compare the outcome of our study with the
results we obtained from the 2015/2016 monitoring campaign on this source.
