That is honestly a truly one-of-a-kind reason that I've heard of
for kicking out a bus from its perm svc in so many years of bus
spotting. 
On another note, wouldn't it have been easier if SLBP just
simply upgraded the slot and deploy a Wright on the slot? (Instead
of running 9364S till scrap..) It's not like SLBP is short of
Wrights nowadays anyway...
Yup my BC fren told me every Monday come uh whoever morning duty
that bus one always cannot on the System after it sleep for like 2
days on the weekend? IDK.
And as for why not replace direct with WEG is because that slot
is a NWAB timing, previously they put in 3671U is for testing after
that they think that bus ok throw it to S shift then swop 9648 back
to this slot cos 3671U was relatively new so they didnt want to
spoil the bus so fast by letting it run A/P.
Maybe after 9364S scrap or earlier they will revise the
timetable again? Idk. Either revise that slot to WAB or remain it
and use another VO cover? But i guess will definetely convert to
WAB already bah.
