These two patches:

chan_local_debug_1.4.21.2.patch
chan_local_debug_1.4.27.1.patch

add extra debugging information to the local channel bridging process.
This is useful to help figure out why local channels are not resolving.
Once the issues are fixed this patch should be reverted and it will
cause a reduction in performance.

Besure to apply the patch that best matches your asterisk version.