Update - We're continuing to reduce the error rate towards elimination. We're now experiencing a much smaller volume of errors shown to people checking in (1 in every ~30 people checking in).

Refreshing once (in some cases a couple of times) in all cases now appears to be a viable solution for people checking in. We're continuing to work on eliminating the issue entirely.
Jun 8, 10:45 AEST

Update - We are continuing to investigate this issue. It appears to have not impacted the Data Download Portal as initially identified.

It has been verified that in most cases people can refresh their phone (might require a couple of refreshes) to continue their checkin experience if they haven't received an error.
Jun 8, 10:27 AEST

Update - Over the last hour we have reduced the error rate to ~1 in 8 people checking in (previously ~2 in 3 people checking in). Still working through a viable solution.
Jun 8, 10:18 AEST

Update - When initially discussed ~2 in 3 checkins would fail on the first submission. The data would be stored but the checkin summary page would not display on the checkin summary page and instead show a 502 error. We're actively working to reduce and resolve this issue.
Jun 8, 08:51 AEST