I merged three Dependabot PRs back to back, to “get it over with.” Each one redeployed the site. Each deployment takes longer to actually finish than the GitHub Action takes to report success.
I found this out by watching the exact same error happen three separate times, at three separate confidence levels of “surely not again”:
Sorry, deployment 38 is in progress for service "mediocresecurity".
Please wait for it to complete before trying again.
None of it was the version bumps’ fault. All three were just re-runs of the same job, spaced further apart each time, until Lightsail actually caught up. The fix, eventually, was patience — which is not a thing I have a natural supply of.