There appears to be an issue with the Galaxy S9 and Galaxy S9+, but fortunately, it isn't to do with the battery.
As Android Central reports, a number of S9 and S9+ owners are reporting "dead spots" occurring on their mobile phone's touchscreen. Locations near the top of the touchscreen are apparently ending up being unresponsive and no longer detect taps or swipes. Resetting the phone does not repair the issue.
Samsung released a statement which mentions that the company is aware of "a limited number of reports of Galaxy S9 and S9+ touchscreen responsiveness problems." We have no idea how limited those reports are, but you can bet Samsung is already examining the production process and parts for its handsets in case there's a problem. The last thing it wants is tens of thousands of mobile phones needing screen replacements.
So far, it seems likely this is a touchscreen fault on the new Galaxy handsets and therefore Samsung will hopefully repair it free of charge.