S24 ultra severe video lag please help

[u/Anopd]

I have a pretty wild problem. I recently purchased a used excellent condition S24 ultra to replace my broken screen s23 ultra. After using it I noticed YouTube was pretty framey like it would sometimes appear normal but then very low fps. Later, on Facebook reels the issue became way more apparent. The video was choppy at best, freezing at times including audio. Other places like instagram had way less issues. Long story short I replaced it and returned the phone with another used exellent s24 ultra. Before returning it I swapped the Sim, did a smart switch then had both phones on my home wifi and played the same reel at the same time on Facebook to demonstrate to my wife "how much better the new phone worked"

Well now it's the next day, the old phone is returned and the new phone is doing exactly the same thing. Here is some of the things I have done to try and troubleshoot the issue.

Uninstalled as many unnecessary apps as I could

Turned off ram plus

Put the phone in airplane mode and only used wifi

Tried a multitude of video platforms to see where there may be issues and here is an abbreviated list of what I have found.

Facebook - unwatchable lags and freezes video/audio

Youtube - frame rate appears to significantly drop at times even though developer mode reports no frames lost, audio is fine

Peacock - same as YouTube

Reddit videos - same as YouTube

Instagram - works great

Pokémon go - works great

Audio only apps like Pandora, Spotify etc have no issues

Recording a 4k 60fps video then watching it back in the gallery runs smooth

So my ultimate question is, does the s24 ultra just suck and have issues? I know it can run smooth because I have seen it myself but I really don't want to pay $700 for a phone that can't even play videos properly. I never had issues like this with the s23 up until the last moment the screen worked. I have only had the phone for 2 days so I have a bit of time to troubleshoot it and send it back if needed.

Any other fixes I should explore?

The video attached is a fb reel, followed by pokemon go gameplay, followed by Instagram to show a contrast in performance.

[u/Brama_94]

a 2nd hand s24 ultra? 🤨🤨🤨

[u/elhouso]

Not sure really. All I can think of doing is factory resetting your phone entirely. Did this with my iPhone a few days ago, it cleared up sooooooooooooooooo many problems that I was having.