Atode uses Apple’s default text selection, which can sometimes be unreliable. For example, the behaviour (and issues) are similar to when text is selected in the standard Safari browser.

What usually works best is to:

1. Long press on an individual word
2. Adjust the selection handles afterwards

It has already been improved in recent OS versions, it’s recommended to update your device to the latest system version. There will likely be more optimizations in upcoming platform updates. Please report this issue directly to Apple for it to be prioritized:
https://www.apple.com/feedback/