[Solved] Error encountered while writing: An unexpected error occurred. Please contact your System Administrator for assistance.

A new developer is getting the following error when attempting to load-data:

<EXTR:ModelList xmlns="http://www.onenetwork.com/Platform" xmlns:ZBKS="http://www.mybooks.com/Bookstore" xmlns:EXTR="http://www.expensetracker.onenetwork.com/ExpenseTracker">
    <ValueChainId>9123</ValueChainId>
    <CustomModelName>Standard EXTR.Transaction</CustomModelName>
    <ActionName>ERROR</ActionName>
    <Error>
        <MajorCode>80006</MajorCode>
        <MinorCode>1</MinorCode>
        <Message>Error encountered while writing: An unexpected error occurred. Please contact your System Administrator for assistance.</Message>
        <MessageArg>An unexpected error occurred. Please contact your System Administrator for assistance.</MessageArg>
    </Error>
    <EXTR:Transaction>
        <EXTR:Error>
            <MajorCode>80006</MajorCode>
            <MinorCode>1</MinorCode>
            <Message>Error encountered while writing: An unexpected error occurred. Please contact your System Administrator for assistance.</Message>
            <MessageArg>An unexpected error occurred. Please contact your System Administrator for assistance.</MessageArg>
        </EXTR:Error>
        <EXTR:LastModifiedUser>DefaultBookstoreValueChainAdmin</EXTR:LastModifiedUser>
        <EXTR:LastModifiedDate>2021-06-01T10:51:48-05:00</EXTR:LastModifiedDate>
        <EXTR:ValueChainId>9123</EXTR:ValueChainId>
        <EXTR:Name>Kroger</EXTR:Name>
        <EXTR:PriceAmount>34.99</EXTR:PriceAmount>
        <EXTR:PriceUOM>USD</EXTR:PriceUOM>
        <EXTR:Category>Food</EXTR:Category>
        <EXTR:State>Entered</EXTR:State>
    </EXTR:Transaction>
    <EXTR:Transaction>
        <EXTR:Error>
            <MajorCode>80006</MajorCode>
            <MinorCode>1</MinorCode>
            <Message>Error encountered while writing: An unexpected error occurred. Please contact your System Administrator for assistance.</Message>
            <MessageArg>An unexpected error occurred. Please contact your System Administrator for assistance.</MessageArg>
        </EXTR:Error>
        <EXTR:LastModifiedUser>DefaultBookstoreValueChainAdmin</EXTR:LastModifiedUser>
        <EXTR:LastModifiedDate>2021-06-01T10:51:48-05:00</EXTR:LastModifiedDate>
        <EXTR:ValueChainId>9123</EXTR:ValueChainId>
        <EXTR:Name>Bank of America</EXTR:Name>
        <EXTR:PriceAmount>250.0</EXTR:PriceAmount>
        <EXTR:PriceUOM>USD</EXTR:PriceUOM>
        <EXTR:Category>Transportation</EXTR:Category>
        <EXTR:State>Entered</EXTR:State>
    </EXTR:Transaction>
    <EXTR:Transaction>
        <EXTR:Error>
            <MajorCode>80006</MajorCode>
            <MinorCode>1</MinorCode>
            <Message>Error encountered while writing: An unexpected error occurred. Please contact your System Administrator for assistance.</Message>
            <MessageArg>An unexpected error occurred. Please contact your System Administrator for assistance.</MessageArg>
        </EXTR:Error>
        <EXTR:LastModifiedUser>DefaultBookstoreValueChainAdmin</EXTR:LastModifiedUser>
        <EXTR:LastModifiedDate>2021-06-01T10:51:48-05:00</EXTR:LastModifiedDate>
        <EXTR:ValueChainId>9123</EXTR:ValueChainId>
        <EXTR:Name>City of Farmers Branch</EXTR:Name>
        <EXTR:PriceAmount>90.0</EXTR:PriceAmount>
        <EXTR:PriceUOM>USD</EXTR:PriceUOM>
        <EXTR:Category>Utilities</EXTR:Category>
        <EXTR:State>Confirmed</EXTR:State>
    </EXTR:Transaction>
    <EXTR:Transaction>
        <EXTR:Error>
            <MajorCode>80006</MajorCode>
            <MinorCode>1</MinorCode>
            <Message>Error encountered while writing: An unexpected error occurred. Please contact your System Administrator for assistance.</Message>
            <MessageArg>An unexpected error occurred. Please contact your System Administrator for assistance.</MessageArg>
        </EXTR:Error>
        <EXTR:LastModifiedUser>DefaultBookstoreValueChainAdmin</EXTR:LastModifiedUser>
        <EXTR:LastModifiedDate>2021-06-01T10:51:48-05:00</EXTR:LastModifiedDate>
        <EXTR:ValueChainId>9123</EXTR:ValueChainId>
        <EXTR:Name>Netflix</EXTR:Name>
        <EXTR:PriceAmount>15.99</EXTR:PriceAmount>
        <EXTR:PriceUOM>USD</EXTR:PriceUOM>
        <EXTR:Category>Entertainment</EXTR:Category>
        <EXTR:State>Confirmed</EXTR:State>
    </EXTR:Transaction>
    <EXTR:Transaction>
        <EXTR:Error>
            <MajorCode>80006</MajorCode>
            <MinorCode>1</MinorCode>
            <Message>Error encountered while writing: An unexpected error occurred. Please contact your System Administrator for assistance.</Message>
            <MessageArg>An unexpected error occurred. Please contact your System Administrator for assistance.</MessageArg>
        </EXTR:Error>
        <EXTR:LastModifiedUser>DefaultBookstoreValueChainAdmin</EXTR:LastModifiedUser>
        <EXTR:LastModifiedDate>2021-06-01T10:51:48-05:00</EXTR:LastModifiedDate>
        <EXTR:ValueChainId>9123</EXTR:ValueChainId>
        <EXTR:Name>Del Friscos</EXTR:Name>
        <EXTR:PriceAmount>99.99</EXTR:PriceAmount>
        <EXTR:PriceUOM>USD</EXTR:PriceUOM>
        <EXTR:Category>Food</EXTR:Category>
        <EXTR:State>Confirmed</EXTR:State>
    </EXTR:Transaction>
</EXTR:ModelList>

The Action in question does not have a workflow set for it. It is a system generated Action, so it cannot be deleted and re-created.

The server log is attached.

What is the best way to resolve this issue?