I've been doing on-going client work for someone using BitBucket and for weeks it feels like every other day has an outage related to their pipelines (CI) feature (the thing I happen to be working on).
It was constant banners about service disruption. There's a lot of UI outage related issues too, like the pipelines page starting to show a new build but never updating any of the progress until you reload the page -- which sounds like some type of API outage somewhere. I'm not sure if that gets reported as an outage but it makes using the platform not fun.
Plus of course the service was so damn slow that using it was a daily pain.
I imagine that there are stability issues that any provider will have to deal with as they scale to account for the masses.