Unable to sign into Wordpress admin sometimes


I've been having a weird issue with this 1 website for the last few weeks and I'm baffled as to what the issue could be.

The website login page is ayesha.i2w.co.in/wp-admin and most of the time you can just visit that page, and login without any issues.

But, occasionally on 1 computer when you visit that page, you will get a 404 error (like so https://www.dropbox.com/s/axtbjh2cit3rsgv/url.png.PNG?dl=0)

But other people can still log in.

If say, my business partner is getting that error, I am still able to log in fine and visit that URL.

And vice versa, if I get that error, he is still sometimes able to log in.

I'm not really sure how to start debugging this because all the results on Google are for when it is impossible to log in always because the file is deleted or something, but in this case it seems to be random. Usually you wait for a few hours, you'll be able to log in again etc.

It could be possible that it is because there are multiple people trying to log in at the same time? some sort of security feature?

Any help is appreciated with this, I'm really lost haha