Articles + uses Apple's default text selection, which can sometimes be unreliable. The behaviour (and issues) are the same as when you for example select text in Safari browser.
What usually works best is to:
- Long press on an individual word
- Adjust the selection handles afterwards
There will likely be some optimizations in an upcoming iOS platform update. Please report this issue directly to Apple for it to be prioritized:
External Monitor (Mac 11.4+)
Due to a bug in macOS 11.4+, layout rendering for some Mac Catalyst apps no longer works as expected when an external monitor is connected. While the correct content is initially displayed, it breaks the more you scroll or change a page.
According to Apple, a system-level fix is required. It should now work again with macOS 12, but unfortunately a patch for macOS 11 will not be released.
There is no workaround available and you will need to either update to macOS 12 or disconnect external displays. Please report this problem directly to Apple: