Tracks - Challange NOT marked as completed?

I’ve inputted and submitted the flag for the “Lame” challenge within the “Beginner Track” and yet the progress marker (refer to the screenshot – marked in red) is NOT set as completed.

Am I missing something? Why wasn’t this challenge marked as completed?

Additionally if I try to reinput the flag then the following error message is displayed: “Lame root is already owned”.

So regarding the original question: is this a glitch or a feature?

Deat Gowzef;
I think you might have found a solution already, but to anyone who arrive to this post.
Always when starting a completed Box look for “Official HTB Walkthrough”.
You will find useful information there.
Nobody born knowing how to do the things, at the beginning try to collect as many information as possible. Everyone pass throw this while starting, there is a lot of new information and we are trying to go faster to gain a level, but there is no competition, take your time.
You are in the right place to start learning.