Can you share a bit more info about your app? Is it using Dockerfile or Buildpack?
Is it possible to see your Dockerfile?
And finally, can you share your app console link so I can have a closer look?
It seems you have a Dockerfile in your project, is there any reason not using it and using buildpacks instead?
We have regularly issues with Buildpacks as we heavily depends on Heroku images. We recommend using Docker for production / anything serious and Buildpacks for quick tests eventually.
Is there a way for you to use Docker instead?
Buildpack is good since it’s less work but it’s a bit too magic and more difficult to operate behind the scene. If you can move to Docker, I strongly advice for it