Update docs

README.md

@@ -12,3 +12,10 @@ Copy image from src to dst.
 | src-creds            | credentials with format: [USERNAME]:[PASSWORD] to pull source image      | username:password                                         |
 | dst-image            | destination image with tag to copy to                                    | registry.cn-hangzhou.aliyuncs.com/coscene/platform:latest |
 | dst-creds            | credentials with format: [USERNAME]:[PASSWORD] to push destination image | username:password                                         |
+
+## Troubleshooting
+
+1. You MUST ensure that the content of the credentials `[USERNAME]:[PASSWORD]` DOES NOT contain any colons(`:`) other
+   than the separator one. Otherwise, it is likely that the registry will not be accessed correctly. Of course, we can
+   extend the `cred` parameters to `registry`, `username` and `password` to avoid this problem. But this increases the
+   complexity of this action.