I also suspect that it is some kind of SW bug.
Also, it is strange that this problem always appeares in certain timeslots only and not in entire E1. If I lock these faulty TSL’s then everything is OK.
So, thats why I am asking if anyone else has experienced this kind of fault in their network, because if it is SW bug then it should appear in many networks.
There is also possibility that it can be something in our transmission netwok aswell.