TL: DR
Due to a change introduced in Kusama with v0.9.34 Update, the UnitsPerSecond value for xcKSM for the XCM-Transactor Pallet needs to be multiplied by 10.
Summary
The introduction of V0.9.34 in Kusama changed the concept of CENTS. This means that the value set in storage for UnitsPerSecond for xcKSM in the XCM-Transactor pallet is insufficient to pay for execution in Kusama.
This value needs to be multiplied by 10x, as CENTS is now defined as 10^12/3000 instead of 10^12/30000. More info can be found on the Moonbeam Docs site.
Proposal
Proposal #123with the following hash: 0xc61f0598b03da2ac0260f1c28cf6f0b258e98fe20c011a20319e88d146f98c6b
Technical details:
The call used is xcmTransactor.setFeePerSecond(assetLocation, feePerSecond), where assetLocation is KSM multilocation ({parents: 1, interior: here}), and the new unitsPerSecond value is 414851773500.
If you are interested, the hex-encoded call data for this proposal in Moonriver is:
0x6b070101003cb41797600000000000000000000000