Reparse bbcodes destroys topic subject (when thread had been split, as it seems) by copying empty ph

After I reparsed my db, I noticed that some postings have lost their subject in phpbb_topics.topic_title.

I can not be 100% sure about this, but it seems that this only affects postings which had been split up parts of other threads (in my old board which I converted) before.

These postings (which then are the first of the (now new) thread) have no own entry in phpbb_posts.post_subject (in contrast to the "pure" first-postings). While reparsing, as it seems, the parser writes this empty topic subject into phpbb_topics.topic_title and so overwrites the correct topic title.
This results in an empty thread title in the board.

I checked this by comparing some of these posting before and after reparsing.