Extremely comfortable, but what's going on just to the sole?

I buy many years Birkenstock shoes and was always a fan of them. The shoes are super comfortable, relaxing for the feet, no question. But (but I bought elsewhere) in this pair that I have given away, as well as in mine, the rubber sole is starting over again. A returning thanks to Amazon, as always, a very customer friendly seller, would have been no problem. But a good Schuhreparteur has helped and it repaired. Actually I do not want to give up the good shoes. The quality is usually very good. But Birkenstock should above all continue to offer the time-tested super quality at the high price.