@Melburnian1 what is going on with all of these cancellations and delays with the Dash 8 300s MEL-MQL SYD-MQL ... flights are reasonably full! Bring back the Q400!
Apologies, I can't answer you. Maybe milehighclub, a QF staff member, can assist.
FlightRadar24 doesn't always record the Q300s well 'after the event' (if one is checking say an hour after the flight landed for flight history over a week), but using other sites like FlightAware allows one to mostly see what occurred.
Timekeeping can be poor. Autumnal/winter fogs at inland rural airports can be one hindrance.
On Wednesday 5 May, Q300 VH-TQG operated QF2192, the 1715 SYD up to distant MRZ that did not become airborne until 1810 hours, arriving at 1941, 51 minutes tardy.. It arrived back in SYD as QF2193 at 2130, 45 minutes late.
Today, the same Q300 was initially on another SYD - MRZ, the 0710 hours (QF2180) that took off at 0910 but did not arrive in Moree until 1140 hours, 175 minutes late. There may have been fog. The plane couldn't recover all this lost time when flying back to SYD, then a newish QFd route to OAG and back, and flying again to MRZ and back to SYD, arriving at 2127 hours, 42 late.
VH-SBT on Tuesday 4 was on QF2059, the 1850 hours MEL - DPO that departed about 45 minutes late, but diverted back to MEL - fog? It hasn't been used since and may go some way to explaining problems with the MQL flights.
QF2031 from ARM to SYD this afternoon arrived at 1855, 50 minutes tardy with Q300 VH-TQH.
The Airfleets site suggests only a couple of the Q300s are stored (i.e. out of use) but while I didn't record them, four or so (at least) haven't been recently used. This could be due to lack of passenger demand, maintenance, insufficient (re)qualified crews available given the COVID-19 hibernation or some other reason.
Five Q300s are more than 20 years old. If maintained properly (which QFd would do), it has little or no bearing on safety but despite a cabin refurbishment in recent years, like the ZL SAAB340Bs they're probably in an ideal world due for replacement. But others with greater knowledge suggest it's difficult to find a suitable model/design to replace the SAABs of the competitor, so maybe QFd's turboprops have a similar problem.
On Friday 7 May 2021, the only QFd cancellations ex MEL I can see thus far are QF466/QF474 at 1630 and 1730 hours - peak afternoon time - to SYD.