What causes a 404 error in the console?

Question

Google Chrome

I welcome everyone!
Wrote a simple script to enter the site and follow a specific link.
The script works properly, but there is one thing. When I open the console on the page where the bot fills in the data, a 404 error appears in the console.
This error does not always appear, I don’t know what causes it to appear, if anyone knows, please tell me why it appears and how to fix it.
Thanks in advance

UPD: sometimes this error pops up: