This sounds like a user problem and definitely not a worldwide Canvas problem. This user should close extra tabs in their browser, reset their browser, close every single open program, actually restart their computer completely, or use a different one entirely. Even though the user says they have used multiple computers, I assume the norm, which is that they are just switching between 2 computers they own, and not using a computer they have never used before. The user may have an extension installed (that installs automatically whenever they sign in to Google Chrome, for example) that is using a lot of CPU or disk resources, and is drastically slowing the input. Or, the user has a virus on both computers, which would also slow input.
There are many variables in play, but we know that the issue is not a Canvas-wide issue. We could assume it is not an institutional-wide issue, as you have not indicated that you have this problem, and you admit it is the first time you've heard of it. Therefore, it is most likely a user issue.
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