hmlinter stuck running for 24h

We're running into a situation where the HM Linter check has been stuck on running for almost 24h now. We have about twelve total commits in that state since yesterday, so it looks like there's a consistent issue with the run. There might be some issue with Lambda that isn't informing GitHub of the execution failure. Is there any way to debug this on the user end? It's blocking Pull Requests, so we might need to remove the check until it's resolved.

Steps to Reproduce
1. Push a commit to GitHub.
2. Go to the automated check details

Expected Behavior: Historically, the check finishes in less than 5 minutes.
Actual behavior: Twelve commits running for almost a day.

Start by reproducing the issue with a GitHub commit and inspect the automated check details, then investigate whether the Lambda execution reports completion or failure back to GitHub. Done means HM Linter checks finish or fail within a reasonable time instead of remaining running indefinitely, so pull requests are no longer blocked.

Written by the indexing model from the issue text.