Errors on tables with a composite public key

[thruflo]

Just testing a source using the Share Explore and the HTTP request worked but the interface errored due to a composite primary key.

Repro would be to sync a table using a composite primary key.

[KyleAMathews]

Just ran this migration on a site:

CREATE TABLE order_items (
    order_id INTEGER,
    product_id INTEGER,
    quantity INTEGER,
    PRIMARY KEY (order_id, product_id)
);

INSERT INTO order_items (order_id, product_id, quantity) VALUES
(1, 101, 2),
(1, 102, 1),
(2, 101, 3),
(2, 103, 4),
(3, 102, 1);

And shape explorer displayed this:

So it seems like some other issue?