QF9 from PER to LHR used to be very good with punctuality but partly due to what 789nerd (and I) suggest above, it's slipped somewhat.
On Thursday 23 June, this 1515 hours from MEL-originating flight took off at 1822, arriving in the Golden West at gate at 2030 hours, 185 minute sbehind schedule. Takeoff for LHR for aircraft B789 VH-ZNE occurred at 2219 (pushback schedule says '1850') so expected arrival today (Friday 24) becomes 0754, 169 minutes past the allotted.
The southeast bound QF10 from LHR arrived PER yesterday (23 June) at 1301 hours, 81 minutes late, and subsequently was at its designated MEL gate by 2013 hours, 93 minutes tardy, the aircraft being B789 VH-ZNG. Today (24) the same flight has VH-ZNI. It arrived PER at 1241 hours local time, 61 late and has taken off for distant MEL at 1428, so if arrival at gate occurs at the expected 1936 hours, that will be 56 minutes behind the timetable. Thankfully it won't have lost further time since the Perth arrival.
Last night, A388 VH-OQD on QF1 arrived SIN at 2251 hours, 36 minutes tardy. Takeoff for its final sector to London Heathrow was at 0111 hours this morning, so suggested at gate arrival is 0738 hours, 63 minutes tardy.
Southbound, the A380 on QF2 is regularly running an hour or so late into SYD, where arrival is scheduled at the ridiculously early time of 0510 hours, longstanding practice and presumably to do with slot availability in LHR, remembering that these pre-COVID-19 were valuable (and IIRC, able to be 'leased' to other airlines). On Friday 24, VH-OQK arrived 77 late at 0627 hours.
The 23 June departure from LHR (the 2105 hours, VH-OQJ) didn't take off until 2309 so today, expected SIN arrival has become 1904 hours, 99 minutes late. This guarantees a delayed arrival in SYD on Saturday 25 June's early morning.