Getting App Platform to resolve custom domains faster

We are migrating a number of application instances from elsewhere to App Platform. As part of this, we have previously moved all related DNS records into Digital Ocean. They are all A records with TTL of 300 seconds (5 minutes).

When I migrate an instance to App Platform, I first remove the associated A record. The old instance goes offline (expected). I migrate the database, then spin up the new app and assign the domain to it, having DO manage it. DO creates the CNAME as expected and the domain status becomes “Pending”. This process takes at least 5 minutes, so the TTL on the old A record has expired, and this can be verified with dig.

However, invariably, the app fails to generate a certificate for the domain, reporting “Invalid configuration”. I have tried waiting idly, I have tried re-adding the domain to the app in an attempt to get it to try again, I have tried re-deploying the app. It consistently takes 30-60 minutes to resolve - remember, this is production downtime!

I assume App Platform uses a DNS challenge to generate the cert with Let’s Encrypt - why is it taking so long to do so when the DNS changes are quickly propagating according to all other sources? Is there anything about the above process I can change to speed things up?