Lyrics extender line gets too long and goes beyond the last note.

When I add an extender line to lyrics for a few long notes (Shift+underscore), it should stop at the last of those notes. This usually works. However, in some cases the extender keeps extending the following measures, till the very end of the score. In other words, it does not stop where it should be. Please see the attached example.

This seems to be a Voice problem. As seen, the extender for the lyrics of the measure above is working. That extender is on Voice 1. I guess the problem is that the extender in the lower measure with the lyrics of Voice 2.