@DeborahNicholson I see, when i take your desciption and pull a tab to the right side of the plus, for the first time in a new browser session, the Opera One browser freezes for a split second, even on the newest version, acting like he runs into a memory leak. I've also seen spikes in RAM usage at that moment, but since my system is already running other applications i can't definately say that those are caused by Opera One itself.

https://app.screencast.com/lythfjmJPR34W

Thank you and i hope this issue gets looked into once more, have a great day aswell, Deborah.

@DeborahNicholson Hello, yes, since the update i never had any Opera One crashes again. Currently running on version 112.0.5197.39 and as of writing this answer the borwser seems to have another update ready (112.0.5197.53).

This bug seems to have just been fixed with the rollout of the latest version of Opera.

I was just recording a video of the bug occuring on Opera 111.0.5168.25, but the browser just updated to version 111.0.5168.43. Now i can no longer reconstruct the bug. The tabs seem to respond way faster now, too, and drag & drop of tabs doesn't cause the browser to stutter any longer.

My method of reconstructing the error in 111.0.5168.25 was:
Open a new instance of Opera (e.g. private surfing mode).
Open a few Opera tabs with different sites, just so they load content from other websites.
Open new, empty tabs and move them in the bar, until the crash occures.