The next runtime upgrade v0.4.0 requires polkadotXcm.safeXcmVersion to be configured properly to be able to send XCM, as pallet-xcm uses the storage instead of a hard coded value from v0.4.0 onward.
Right now XCMv2 is deployed. The message format V1 is the oldest supported version, V2 is the current version. With v0.4.0, XCMv3 is deployed. The message format V1 will be deprecated, V2 will be the safe default and V3 will be the most recent version.
⚠ Not configuring this value before deployment of v0.4.0 results in the inability to send XCMs.