I have bought a used T2980 from 2021 (labeled on device). I think (hope) it's a T2980.61.
Round about at the end of my 5th ride, suddenly the freewheel stopped working while I was 'driving down' a mountain with above 50 kilometers an hour. When I stopped pedaling, suddenly I was shocked by a loud and anoying noise. Looking to the drivetrain I realized that the force of the flywheel was translated trying to pull the chain into the derailer. I remember it like there was a pulse every quarter of a second. I tried to spin up in order to avoid damage, but the chain already had derailed and was displaced in a nasty manner.
Having dismounted the system I found what I was more or less expecting since I mounted the cassettte. The metal ring that holds the three cogs of the freewheel in place had moved it's opening to more or less the center of one of the cogs and that cog was not in place anymore being the cause of the block.
So I remounted the system with everything in place and the opening of the metal ring centered between two of the cogs. It seems like everything is fine again and the freewheel is working. However. I'm not sure if the drivetrain hasn't taken damage I'm not aware of. I found some flaked off paint beneath the chainstay, but I cannot be sure that it is a consequence of this.
Have you experienced the same issue?
Any ideas what I could have made wrong or about meassures to avoid this in the future?