Good point, Patrick.
I've had to adjust my freqs numerous times on VO-52, but never considered the bird was a bit 'off'.
When the transponder change from the failed Indian-built transponder to the PE1RAH-built unit was made a few months ago, I (and many others) found that we had to raise our uplink frequency 5 to 6 kHz to keep at the same downlink frequency we would use previously. That figure tends to move around a little, so what worked for me last weekend may not be the same for a future pass. Unfortunately, the AMSAT-India group or the Indian space agency have not released details on why the original (Indian-built) transponder stopped working.
The PE1RAH transponder also can't handle high-powered uplink signals as well as the previous Indian-built transponder. If someone is pumping too much power up to the satellite, it will not retransmit anything else from the uplink. But at least there was a backup to the Indian-built transponder onboard, so that the satellite isn't just silently orbiting with a failed transponder.