chronik nng returns a string for the value key of utxos. ecash-coinselect then converts these to int, which TransactionBuilder requires for signing.
When we get to in-node chronik-client, the value key will always be an integer. In general, we should not be explicitly setting something to be a string in this function if we know it needs to be an integer later.
The send method in this page is updated separately in D15519