Product: FileMaker Pro Advanced 17.0.4
OS: Windows 10 w / scaling set over 100% for use with high-DPI screens
Hardware: High-DPI monitor
Description: Web viewer contents in FMPA show at 100% scaling on Windows, even if the system is set to a higher scaling level, such as 200%. This is an issue on high-dpi displays or for people who need things scaled up a bit to see the contents. When this happens, FMPA itself scales to the correct level, but the contents of the web viewer remain at 100% and everything in them appears tiny.
How to replicate: Make a web viewer on Windows with scaling set to a value over 100%, such as 200%. The web viewer contents will be at 100% (and therefore be very tiny) while everything else is properly scaled to 200%
Here's a screenshot with a web viewer on the left and a browser on the right which illustrates this difference.