So, after my DMI was wrapping up and we were just chatting, I mentioned something about troubleshooting/fault-finding (helping my partner fix the heater fan in his car, as I'm a woman and felt an anecdote of me being technical and hands-on was worth dropping in). My interviewers both chuckled and said something along the lines of me not being expected to actually do anything like that when I'm a driver.
When I'd been looking around on here for help with examples that would work with that particular MMI question, a few people suggested driving long distances alone, which is what I used, as I have some experience of that. I think the question is open for sure, but I feel like an answer where you can demonstrate working alone for long periods, being able to focus and concentrate for long periods while doing something safety critical, etc., would be a good option.
But, I think if you can articulate your troubleshooting the right way, and demonstrate that it ticks the boxes they are looking for in the MMI (methodical, working to procedure, tenacious, etc.), then it's a totally valid answer.