I have never seen something like that, where database details are lost (reset to nothing/defaults).
I only know of one issue, that can happen on multi-instances, when editing the database details, then some of the instances might hold on to the previous details until restarted.
Are you using firewall to allow only specific IPs from accessing your database? If yes, did you add all 3 IPs? IP to whitelist for Metabase Cloud instances