This is an issue with libsdl1.2 version 1.2.14 that the wesnoth team found out a while ago and discussed with libsdl upstream developers already. The fix for it unfortunately isn't easy so somehow I fear it will take a while to get fixed.
Given that the libsdl1.2 version 1.2.13 was causing other troubles in Ubuntu the sync still happened. It's hard to decide which issue is "more" relevant.
This is an issue with libsdl1.2 version 1.2.14 that the wesnoth team found out a while ago and discussed with libsdl upstream developers already. The fix for it unfortunately isn't easy so somehow I fear it will take a while to get fixed.
Given that the libsdl1.2 version 1.2.13 was causing other troubles in Ubuntu the sync still happened. It's hard to decide which issue is "more" relevant.