In development mode exist user unfriendly error message

ENV Development mode How to reproduce this error:

1. `sh ./scripts/fast-start.sh`
2. `cd dev/prod && rushx dev-server`
3. stop all docker-containers
4. try to enter with credentials "user1/1234"

While you want to enter the system with credentials that describe there user/customer could not understand the main issue

Current error message:

**Unknown error: JSON.parse: unexpected character at line 1 column 1 of the JSON data**

My offer to use the more precise description of the problem/bug with the current status:

**Unknown error: Failed to fetch: 504 Gateway Timeout**