A variety of errors in the Mobile Backend Starter Sample application

Question

I installed the Mobile Backend Starter Sample app from the Google Cloud console. An android client application can be used as a chat client. When I installed it the first time, I got 404 NotFound, a JsonParseException.

I solved this by reDeploying 2-3 times.

Then it worked for 5-6 hours, after which I encountered the 503 Service Unavailable 503 error. I tried to redistribute, but I returned to the 404 NotFound error.

Am I doing something wrong?

Yes, I changed PROJECT_ID in my Android client code.

Is ReDeploying the only solution over and over again?