LMS and Course Completion Issues

I doubt it is the way that you set up the trigger button, given that the majority of the population successfully completed it (nearly 90%, according to your figures). Additionally, since it doesn't sound like it's happened before now, that would also point toward the LMS being the culprit.

There are all sorts of factors that could cause this type of issue, with different LMSs than Workday. If the failed learners are in remote (non-corporate office) locations, and accessing the training via a range of VPN connections, any one of these could experience drops or glitches. If the learners are not telling you the complete truth ("well, it really did time out on me twice while I was refreshing my coffee and taking a bathroom break, but I told you that I was at the screen the entire time"), that could be another factor.

The LMS could have had its own momentary down period, or have recently installed updates, or... You get the picture.

You may consider building in a "print results" button next time, or a word of advice (take a screenshot) if learners are concerned they may experience this behavior in the future. But I don't think you configured anything incorrectly.

Good luck!