I'm on Lemmy.world & using the eternity app I haven't had any real issues yet but it's only been about 2 months for me since I started using this platform.
We at SDF had some outgoing federation issues recently, and we weren't the only ones. I.e., I'd post or comment something and check from any other instance, and it was like I never posted/commented at all. Fortunately, it seems to have gotten fixed over Christmas Eve.
Also, my original instance (vlemmy) literally deleted itself in July.