So, I submitted a ticket for this issue, I was told this could be due to forwarders, forwarders/alias may be having some restricted special character or something due to which, this is happening.
In my case it was a cPanel to CWP migration.
I took a backup of forwarders, alias table in postfix database (use phpMyAdmin or from command line).
Deleted all forwarders from admin panel as suggested by support and list email accounts in user panel started working.
Added forwarders back, manually this time, all is working fine.
Hopefully this may help someone facing similar issue.