@Developers: this may happen if Hibernate didn't update the indices while removal of the previous sections. If the order is still: 3,4,5, then first elements will appear as nulls in Hibernate list.

Julia Atlygina, is that reproduced from time to time or since then it was okay?

Stanislav Bashkyrtsev we haven't got steps to reproduce, database were dropped several times, issue wasn't reproduced anymore but I don't think it is really fixed. We just need help for investigation from developers side

Do you have plan how to find it? I mean if I give you a developer, will you be able to formulate what you want from him?

Where is a dump attached; I need someone who know it from the "code side" to understand how it was introduced. Note, that we have no ideas what actually happends, just several sections become 'null'.
Perhaps problem was connected with simulteniously editing by several users but we didn't reproduce it.