UnseenMind That's a great idea - I'll give that a go and report back. Only problem is that I don't know how reliable a test will be my side. I'm on a crappy 25mbit connection here in the UK. Definitely worth a try though.
Interesting that you've not seen the problem on the Series S. I played a little tonight and the menus were so unresponsive at times that I couldn't even vote for the map I wanted to play before the timer ran out. It's a pretty new Xbox so I'd be surprised if it were hardware-related, especially as no other games have this problem.
It'll be good to know if other Xbox users are seeing unresponsiveness and stuttering on the menus, as that points to optimisation being required. I'm starting to wonder if there's something odd going on with the network in some way. It's not a problem with the ping, as that's sitting at around 19ms.
The locker is another good test area where I see some stuttering. If you try on an outfit on, it lets you run around while wearing it. Just doing the usual everyday moves, every now and then the animations will pause for around 100ms) or miss button presses. It's a small delay, but definitely noticeable. I've seen this on the Steam Deck too, and this surely can't be network related.
Definitely something odd going on performance-wise as the Series X should be able to handle this, especially if it's all good on your Series S.
I tried out the Steam Deck again today and was positively God-like with my heavy punches. When I moved to the Xbox a bit later I hardly landed a single one. They definitely feel different, but that's not something I can capture in a video.
But, all of this, I don't feel it's game-breaking (at least for me). I've kinda learned to adjust my timings to compensate.
Thanks for your inputs on this!