Lesson editor does not shows pages, possible for jumps.
Applied patch resolves problem
Same problem but for moodle 1.9.10
Thanks for reporting this.
I'm closing this issue because I believe it affects only Moodle 1.9, which is now unsupported (except for serious security issues). This issue, and the provided patch, will remain here in case other users have the same problem.
If you haven't already done so, I encourage you to upgrade to a supported version.