@skraw sorry for barging in from the side, but you describe partial site reply of “30 seconds” → this sounds like you’re running into some brute force protection throttling which could be associated with an incorrect or missing trusted proxies setting in your config.php… this is merely a hunch!
its clear you’re not using the snap, but similar has been documented How to manage security brute force protection and throttling in Nextcloud snap and may give you a nudge in the right direction?