So I finally caught a bug in the act. Yay!

Oh, wait.

That means not only did I get the visual bug but also I lost points for the correct answer on the second question.
The call to submit the answer took
10218ms
, all of which was waiting for the response. The status code returned was
500 Internal Server Error
. So the response time was too long to be able to use the solution I suggested earlier, as the question is already ended when the error is returned.
Response headings
Code:
HTTP/2.0 500 Internal Server Error
x-cloud-trace-context: 0046d7de691d7f994945cf350709d66b
date: Tue, 19 Nov 2019 18:03:14 GMT
content-type: text/html; charset=UTF-8
server: Google Frontend
x-iinfo: 2-40464395-40464396 NNNN CT(0 0 0) RT(1574186584373 0) q(0 0 0 -1) r(102 102) U6
x-cdn: Incapsula
content-encoding: gzip
X-Firefox-Spdy: h2
Response content
HTML:
<html><head>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<title>500 Server Error</title>
</head>
<body text=#000000 bgcolor=#ffffff>
<h1>Error: Server Error</h1>
<h2>The server encountered an error and could not complete your request.<p>Please try again in 30 seconds.</h2>
<h2></h2>
</body></html>
Hopefully this will give the developers something to work with to solve the bug. Not much more for me to do as I can not see what has failed on the server side.