Sign in screen "repaints" before I finish my logon

I use Google Chrome, and when I am at https://files.acrobat.com/ page and start typing my sign in data, suddenly the page "refreshes", cleaning all the data I've just typed.

Then, I need to re-type all the info, and then, the sign in process continues in the right way.

What is happening for the page to be refreshed unexpectedly in the first time?

Thanks.