Just because mechanical failures were reported, does not mean they happened all the time. They happened enough to be considered an issue with the tank design, but not enough to have them completely pulled from service. (Logic)
I don't know if you are correct, I suggest you read up on panther tank wiki page, you might get as shocked as I was.
It was not until 23–29 June 1943 that a total of 200 rebuilt Panthers were finally issued to Panther Regiment von Lauchert, of the XLVIII Panzer Corps (4 Panzer Army). Two were immediately lost due to motor fires upon disembarking from the trains. By 5 July, when the Battle of Kursk started, there were only 184 operational Panthers. Within two days, this had dropped to 40.
General Heinz Guderian a well known panzer tactician wrote the following to Hitler:
Due to enemy action and mechanical breakdowns, the combat strength sank rapidly during the first few days. By the evening of 10 July there were only 10 operational Panthers in the front line. 25 Panthers had been lost as total writeoffs (23 were hit and burnt and two had caught fire during the approach march). 100 Panthers were in need of repair (56 were damaged by hits and mines and 44 by mechanical breakdown). 60 percent of the mechanical breakdowns could be easily repaired. Approximately 40 Panthers had already been repaired and were on the way to the front. About 25 still had not been recovered by the repair service ... On the evening of 11 July, 38 Panthers were operational, 31 were total write-offs and 131 were in need of repair. A slow increase in the combat strength is observable. The large number of losses by hits (81 Panthers up to 10 July) attests to the heavy fighting.
I don't know what else to say, Panther first arrived to the battlefield in 1943. First T-34/85s began production in 1944. On the flip side, Red Army had mass produced their tanks meanwhile Nazi war machine had trouble reaching even 9000 of total produced Tiger 1s and Panthers. So Soviet literally won by spam LOL.
You can check it out yourself, it makes for rather interesting reads.
German armored fighting vehicle production during World War II
Soviet combat vehicle production during World War II
Panther tank
Tiger 1