Since you are using UUPSUpgradable, your contract is deployed as a UUPS proxy.
UUPS proxies do not use a proxy admin, so admin.transferProxyAdminOwnership(gnosisSafe); is not the right way to transfer its ownership.
Instead, just use instance.transferOwnership(gnosisSafe) (your contract needs to implement _authorizeUpgrade() to restrict upgrades to only the owner or another role or address if appropriate)