There is evidence that mail in ballots causes more problems though. However to find unbiased information about it you have to search for articles from a time before it became political.

> Yet votes cast by mail are less likely to be counted, more likely to be compromised and more likely to be contested than those cast in a voting booth, statistics show. Election officials reject almost 2 percent of ballots cast by mail, double the rate for in-person voting.

New York times article:

https://www.nytimes.com/2012/10/07/us/politics/as-more-vote-...

To be clear, it's a prediction of the future. Let's not pretend that predictions of the future are statements of fact.

Next, Twitter will start fact checking every Bigfoot and UFO tweet.