Thank you for your comment. I really appreciate it!
Maybe the cause is really overtraining and overloading. I have considered this, but my physiotherapist or my sports physician will be able to tell me more about it. Especially my exercises on the rings are very demanding for the lower back.
I've always had a slight hollow back, which may increase the cause, as it makes it very difficult to implement the right technique.
I am not just a gymnast, but also a gymnastics coach training a few kids at gymnastics. Thank you for your praise!