Eclipse IDE file search results not reliable?

As you can see from the screen recording here, different files are turning or not turning up randomly across search refreshes by the same search phrase.

My Eclipse version:

Version: 2023-06 (4.28.0)
Build id: 20230608-1333

Search phrase (regex):

->\s*pdo[^\(a-z0-9_]

This is really really unreliable as I rely on code searches for many important tasks. What could be wrong here? How can I make Eclipse give consistent search results?

Tried also a static string search and issue persists.