I have a submission for Poker that uses crates that aren’t found in the test runners. Using a suggestion in another post, I removed the Cargo.lock and submitted the iteration. Unfortunately, that causes a 500 error when trying to view my submission.
Refreshing didn’t work, even after many minutes.
I tried replacing the Cargo.lock file and resubmitting (a minor change to the code was required for “submit” to believe an update was required), but I’m still getting the 500 error. 
Which post? Sounds like bad advice.
How did you “remove” it? By default, Cargo.lock is not part of the submission anyway. This is intended, submitting Cargo.lock only causes more trouble as the versions in the test runner are already pinned precisely.
A 500 error on the website? That sounds like more of a website / infra issue than anything Rust-specific. No matter how messed up a Rust submission is, it should not cause a 500 error on the website.
Did you publish your solution? Can others see this error as well? What’s the precise URL you navigated to, where the error appeared?
Btw. what crates are you using that are not in the runner? Do you think it would be worth including? It’s always possible to extend the list according to user needs. (while keeping an eye on the docker image size)