Yarn install --flat --frozen-lock-file crashes

[joha91]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
When we install our project by yarn install --flat everything works fine (does not ask for some version conflicts and yarn.lock is NOT updated).
When we install our project by yarn install --flat --frozen-lockfile the process crashes with the error:
Your lockfile needs to be updated, but yarn was run with --frozen-lockfile

If the current behavior is a bug, please provide the steps to reproduce.

To reproduce it you can check the ticket: --frozen-lockfile fails
This ticket what solved by removing version conflicts, which is no option for us.

What is the expected behavior?
When yarn does not ask you to resolve some version conflicts when you run without --frozen-lockfile, you also shouldn´t get asked for that / crash the build when you run it with --frozen-lockfile.
Additionally it could allways happen that you have version conflicts and use the resolutions field in multiple projects !! But that shouldn´t make it impossible to run yarn install --flat --frozen-lockfile.
In the small example of the linked ticket it is probably no big deal to resolve the conflict, but in big projects it will be impossible to handle this! --> What we expect would be:
If there are multiple resolution fields for one dependency, yarn should take that one from the "heighest" project.

Please mention your node.js, yarn and operating system version.
node: v8.9.4
yarn: 1.3.2
os: win 10