As initially discussed in the forum post: https://moodle.org/mod/forum/discuss.php?d=276635

Replication steps:

• Create a block in a course and configure it to "Display on page types: any page" and position it in the right hand column.
• Attempt to edit a page within a Lesson module that is a part of that course.
• The block will remain on the right of the page preventing the editing interface from expanding right as expected. Form elements will then overlay blocks on the right of the page.

The fix suggested by Jean-Michel Védrine in the forum post appears to have corrected the issue in my environment. Fix included here for ease of reference:
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I looked at what other modules do when then want to move all the blocks to the left and it seems it's enough to add a single line in mod/lesson/editpage.php

If you are able to edit the files on your Moodle server, you can try to add

$PAGE->set_pagelayout('admin');

after

$PAGE->set_url('/mod/lesson/editpage.php', array('pageid'=>$pageid, 'id'=>$id, 'qtype'=>$qtype));
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