Not even an hour into the Formula 1 season and the reigning champions Mercedes faced their first real hurdle. The team encountered early transmission issues and requires a gearbox change to get the car running again.The early reliability issues faced by the Brackley-based team come on the back of rumors claiming Mercedes faced some reliability issues with their upgraded power unit for the 2021 Formula 1 season.Going to have to keep you waiting a little longer for a proper look at W12... And we had a video and everything. 🙃We have a gearshift problem and are swapping the gearbox to get back out on track for our first real run! 🙏— Mercedes-AMG PETRONAS F1 Team (@MercedesAMGF1) March 12, 2021The early reliability issues faced by the Brackley-based team come on the back of rumors claiming Mercedes faced some reliability issues with their upgraded power unit for the 2021 Formula 1 season.Can Mercedes make up ground?It shouldn't take long for Mercedes to fix the gearbox and get back to running. However, a shortened pre-season test this year could take away valuable track time.With Mercedes slipping up early in testing, it will be interesting to see how the team makes up ground in the coming days and stays on schedule for its preparations for the first race of the season.Max Verstappen suffers a spinYes, finally, here we go 💪 #2021 #UnleashTheLion #F1Testing pic.twitter.com/rQLQatpHpl— Max Verstappen (@Max33Verstappen) March 12, 2021Meanwhile, Max Verstappen had an eventful first hour as the young Dutchman suffered a spin early on. If early impressions are anything to go by, the new Red Bull challenger seems to be a clear improvement from last year's challenger, as suggested by Will Buxton during commentary.Mercedes will surely fix their problems soon, but the reigning champions have already begun the 2021 season on the back foot.