Invalid course module ID

Question

I have installed Moodle with a Master-Slave DB cluster. I have added an artificial lag between the master and the slave of 5 seconds, and when I try to create a new Chat in one course I get the following error:

Error
Invalid course module ID
Debug info: SELECT id,course FROM {course_modules} WHERE id = ?
[array (
0 => '19',
)]
Error code: invalidcoursemodule
Stack trace:

    line 1654 of /lib/dml/moodle_database.php: dml_missing_record_exception thrown
    line 1630 of /lib/dml/moodle_database.php: call to moodle_database->get_record_select()
    line 7443 of /lib/accesslib.php: call to moodle_database->get_record()
    line 1938 of /lib/modinfolib.php: call to context_module::instance()
    line 2446 of /lib/modinfolib.php: call to cm_info->get_context()
    line 2399 of /lib/modinfolib.php: call to cm_info->is_user_access_restricted_by_capability()
    line 2289 of /lib/modinfolib.php: call to cm_info->update_user_visible()
    line 1689 of /lib/modinfolib.php: call to cm_info->obtain_dynamic_data()
    line 1534 of /lib/modinfolib.php: call to cm_info->get_name()
    line 2219 of /lib/navigationlib.php: call to cm_info->__get()
    line 2258 of /lib/navigationlib.php: call to global_navigation->generate_sections_and_activities()
    line 760 of /course/format/classes/base.php: call to global_navigation->load_generic_course_sections()
    line 189 of /course/format/topics/lib.php: call to core_courseformat\base->extend_course_navigation()
    line 2173 of /lib/navigationlib.php: call to format_topics->extend_course_navigation()
    line 1538 of /lib/navigationlib.php: call to global_navigation->load_course_sections()
    line 4295 of /lib/navigationlib.php: call to global_navigation->initialise()
    line 832 of /lib/pagelib.php: call to settings_navigation->__construct()
    line 962 of /lib/pagelib.php: call to moodle_page->magic_get_settingsnav()
    line 393 of /lib/classes/navigation/views/secondary.php: call to moodle_page->__get()
    line 216 of /lib/classes/navigation/views/secondary.php: call to core\navigation\views\secondary->load_course_navigation()
    line 890 of /lib/pagelib.php: call to core\navigation\views\secondary->initialise()
    line 962 of /lib/pagelib.php: call to moodle_page->magic_get_secondarynav()
    line 70 of /theme/boost/layout/drawers.php: call to moodle_page->__get()
    line 1477 of /lib/outputrenderers.php: call to include()
    line 1403 of /lib/outputrenderers.php: call to core_renderer->render_page_layout()
    line 240 of /course/view.php: call to core_renderer->header()


Details from debugger:
Course cache integrity check failed: course module with id 19 does not have context. Rebuilding cache for course 2

    line 502 of /lib/modinfolib.php: call to debugging()
    line 436 of /lib/modinfolib.php: call to course_modinfo->__construct()
    line 2553 of /lib/modinfolib.php: call to course_modinfo::instance()
    line 2194 of /lib/navigationlib.php: call to get_fast_modinfo()
    line 2258 of /lib/navigationlib.php: call to global_navigation->generate_sections_and_activities()
    line 760 of /course/format/classes/base.php: call to global_navigation->load_generic_course_sections()
    line 189 of /course/format/topics/lib.php: call to core_courseformat\base->extend_course_navigation()
    line 2173 of /lib/navigationlib.php: call to format_topics->extend_course_navigation()
    line 1538 of /lib/navigationlib.php: call to global_navigation->load_course_sections()
    line 4295 of /lib/navigationlib.php: call to global_navigation->initialise()
    line 832 of /lib/pagelib.php: call to settings_navigation->__construct()
    line 962 of /lib/pagelib.php: call to moodle_page->magic_get_settingsnav()
    line 393 of /lib/classes/navigation/views/secondary.php: call to moodle_page->__get()
    line 216 of /lib/classes/navigation/views/secondary.php: call to core\navigation\views\secondary->load_course_navigation()
    line 890 of /lib/pagelib.php: call to core\navigation\views\secondary->initialise()
    line 962 of /lib/pagelib.php: call to moodle_page->magic_get_secondarynav()
    line 70 of /theme/boost/layout/drawers.php: call to moodle_page->__get()
    line 1477 of /lib/outputrenderers.php: call to include()
    line 1403 of /lib/outputrenderers.php: call to core_renderer->render_page_layout()
    line 240 of /course/view.php: call to core_renderer->header()

I have tried to use the "latency" in config.php with a value of 5.5 seconds (greater than the artificial delay) to simulate high load on the platform. However it doesn't seem to work as expected.

Any tips?