Assignment

Turning on Debug mode showed this code:

user => Invalid response value detected: theme => Invalid response value detected: Invalid external api response: the value is "yorkville2016responsive", the server was expecting "theme" type
Error code: invalidresponse
* line 424 of /lib/externallib.php: invalid_response_exception thrown
* line 233 of /lib/externallib.php: call to external_api::clean_returnvalue()
* line 59 of /lib/ajax/service.php: call to external_api::call_external_function()

So you can see here, the input value is incorrect. 

Interestingly, if I keep cycling through users, I can see that users that work do not have a theme set in mdl_user.

AHA! I've got it. A bunch of users are set to use a theme that doesn't currently exist on the server, as seen in the above 

yorkville2016responsive

So this theme value is simply busted. Let's go ahead and set every one to any theme that does exist, like boost, our new system theme.

RUNNING: update mdl_user set theme = "boost"

Purging cache...

Results are: COMPLETE SUCCESS! I have fixed this problem.