When receiving the following error there is a simple fix.
This error occurs when there is an abundance of UTXOs with small token values (usual source of those are delegation fees on your node) so the amount of UTXOs needed to add up to the value you want to send makes the transaction too big to be allowed on the chain. This is a common issue on UTXO-based chains.
The solution is to cut down on the number of UTXOs by doing cross-chain transfers (P->X and back), which consolidate many input UTXOs into a single output UTXO. Start with the MAX value and decrease it until the transaction gets accepted. Repeat until everything is transferred, and you'll end up with much smaller number of UTXOs in your wallet.
The wallet also provides the ability to select specific UTXOs for the Balance Source when staking or delegating, so you can use that to pick high value UTXOs if all you need to do is re-stake your tokens.