Scenario:

1. Login as admin, turn debugging on (DEVELOPER level + Display debug messages),
2. Create a course with a backslash \ character included in its full / long name.
3. Add an activity with a due date (e.g. Assignment).
4. Enrol Student A.
5. Log in as Student A.
6. Visit the Dashboard/Timeline page (Moodle 4) or the Dashboard page containing the Timeline block (Moodle 3).
7. Instead of properly loading, Moodle will show a modal with an alert like this:

JSON.parse: bad escaped character at line 1 column 146 of the JSON data
File: https://YOUR_MOODLE_URL/lib/requirejs.php/1660337173/core/first.js
Line: 17
Stack trace:

ln: 6772
https://YOUR_MOODLE_URL/lib/requirejs.php
Renderer.prototype.stringHelper

ln: 7005
https://YOUR_MOODLE_URL/lib/requirejs.php
Renderer.prototype.cleanStringHelper

ln: 8305
https://YOUR_MOODLE_URL/lib/requirejs.php
Renderer.prototype.addHelperFunction/</<

ln: 8035
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderSection

ln: 6836
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderTokens

ln: 9198
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderPartial

ln: 6995
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderTokens

ln: 7634
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderSection

ln: 6836
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderTokens

ln: 9198
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderPartial

ln: 6995
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderTokens

ln: 7634
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderSection

ln: 6836
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.renderTokens

ln: 6556
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/Writer.prototype.render

ln: 10893
https://YOUR_MOODLE_URL/lib/requirejs.php
factory/mustache.render

ln: 10546
https://YOUR_MOODLE_URL/lib/requirejs.php
Renderer.prototype.doRender/<

ln: 30005
https://YOUR_MOODLE_URL/lib/javascript.ph
e

ln: 30307
https://YOUR_MOODLE_URL/lib/javascript.ph
Deferred/then/l/</t<

Also checked: Calendar, My courses page (M4) + Dashboard/Course overview (M3), Recently accessed courses block, Upcoming activities course block - no issues there.