Seems to have happened again, although not sure how serious it was:
C-FNOH, an Air Canada Boeing 787-9 was conducting flight ACA7273 from Toronto/ Lester B.
Pearson Intl (CYYZ), ON to Hong Kong Intl/ Chek Lap Kok (VHHH). On final approach, in visual
meteorological conditions, the aircraft deviated below the glideslope. The glideslope was
reestablished at approximately 900 feet ASL. The flight landed without further incident.