As a fellow Linux laptop (and Bazzite on a HTPC) user, this is a constant risk.

If things are configured correctly (including kernel parameters, etc), you should be losing something like 5% per day on standby. It's very unlikely a hardware issue if you're losing more than that in standby but the battery is fine under normal operation.

Aside from contacting support, I would try a more stable and slow moving distro and see if they have the same issue.