Issue with Azure AD B2C Custom Domains: Unexpected Redirect Behavior and Domain Dependency

Hey everyone, I'm hopeful that there are experienced individuals with Azure AD B2C expertise who can assist me here. I have an Azure AD B2C app with the primary custom domain set as appb2c.b2clogin.com/appb2c.onmicrosoft.com. Additionally, I've added two more custom domains that are linked to my Azure DNS: abc.accounts.platform.com and def.accounts.platform.com. Assuming that my DNS and frontdoor configuration are perfectly set up according to the documentation provided by Microsoft, I encountered an unexpected issue when testing these custom domains with jwt.ms. Specifically, when attempting to log in with the def.accounts domain using any user credentials (let's say user1), it redirects me back to the login page instead of redirecting me to jwt.ms. However, when I log in with user1 through the abc.accounts domain, it functions normally and returns the token through jwt.ms. Interestingly, if I attempt to log in again with the def.accounts domain, it then behaves as expected, returning the token through jwt.ms as it does with the abc.accounts domain. In conclusion, it seems that for each initial login attempt, new users must log in through the abc.accounts domain before being able to successfully log in with other domains. I'm curious as to why this is occurring. Any insights?