Opera recently updated, and it looks like it added tab isolated memory management that now flags nzbget as "Out of memory" - once a day here.
A simple F5 refresh of the tab restores the nzbget view, I now do this each day.
This tab process halt only happens on the nzbget tab, none of the others are affected... for example, I have Emby self-hosted app running in another tab, and remote web pages in others.
Date: 15 Aug 2019
OS: Win 10 x64
Memory usage: 53%
Install path: "C:\Users\<current user>\AppData\Local\Programs\Opera\launcher.exe"
Version:62.0.3331.68 Opera is up to date
nzbget addons, "Completion", "Unzip", "PasswordDet", "FakeDet", "RevName", "SickGear-NG", "IMDBWatchlist" and some RSS feeds are enabled too, therefore, logs are likely larger than the default, and nzbget always lists "Messages (1000)" in the top menu bar.nzbget 21.1-testing-r2311 server-mode
So, nzbget is growing in memory usage until Opera puts a halt on it, perhaps the Logs view is not releasing ?