Multi-account-containers doesn't really break websites in my opinion. It's just like running a separate browser (in fact it's simply a firefox profile under the hood).
What can go wrong is if you've set a certain site to always open in a certain container and another site redirects you to this site. This can happen with Identity Providers like Okta, ADFS etc. They will then open in a different container (the assigned one) and lose context. Especially microsoft services have an annoying habit of redirecting through 25 different URLs on every sign-in. But if configured correctly it's a godsend, you can use this tool to sign into multiple MS tenants at the same time, something with chrome and not even Edge can do right now (switching teams between multiple tenants is a nightmare).
But I don't think it's the multi accounts containers at fault here, it's the user. Just don't do that :P
What can go wrong is if you've set a certain site to always open in a certain container and another site redirects you to this site. This can happen with Identity Providers like Okta, ADFS etc. They will then open in a different container (the assigned one) and lose context. Especially microsoft services have an annoying habit of redirecting through 25 different URLs on every sign-in. But if configured correctly it's a godsend, you can use this tool to sign into multiple MS tenants at the same time, something with chrome and not even Edge can do right now (switching teams between multiple tenants is a nightmare).
But I don't think it's the multi accounts containers at fault here, it's the user. Just don't do that :P