@levelvi Goto the URL opera://settings/userInterface and disable "Snooze inactive tabs to save memory". Then, goto the URL opera://settings/batterySaver and make sure the batter saver is disabled. And, if you're using Opera GX, make sure you're not using any limiters in the GX Control sidebar panel.
Then, install https://chromewebstore.google.com/detail/disable-automatic-tab-dis/dnhngfnfolbmhgealdpolmhimnoliiok. Once installed, goto the URL opera://extensions and make sure "Allow access to search page results" is enabled foe the extension. You can enable it in incognito mode too if you want.
Then, see if that stops Opera from force-reloading the page.