Gap at the bottom after applying Forms patch set 11.1.2.2

After upgrading to Oracle Forms 11.1.2.2 from Oracle Forms 11.1.2.1, the first time we start the session, we get a gap at the bottom (see attached file for details) when we scroll button and we reach the last line. In the same session, after the first time, everything are working fine.

Nothing has changed in the configuration.

Any idea?

Stel