How to reproduce:

1. open Pages App
2. edit e.g. /demo-project/about/history
3. click + to add new Download Link in in the "More information" link list
4. in the Download Link dialog, click Select New
5. in the Asset Chooser, go to the Search field and enter a search term, e.g. "magnolia"
6. hit Enter key

Expected behavior:

The search is processed, so you can select one of the found assets.

Current behavior:

The search is processed, bit the chooser's default action (choose) is immediately fired, so the chooser is closed.

Workaround:

Yes, you can click the magnifying glass icon, or use Tab key instead of Enter, but it is not intuitive behavior - people are used to hit Enter to run the search.