V7 Demo, there is no OK button on Invoices and TypeError: item.master.taxrate is undefined

[platipusica]

Also,

the Detail is missing:

    if (item.quantity.value) {
        calc_track(item);
    }
etc...

which will re-calc the Amount, but it will not adjust the Total!

Also,
when adjusting the Quantity on Tracks/Details, the InvoiceTable Form will error with:
TypeError: item.master.taxrate is undefined

This is also not adjusting the Totals ON the InvoiceTable or on that particular Detail.

TypeError: item.master.taxrate is undefined

This can be seen on:
https://jampy.pythonanywhere.com/

Maybe the solution is to make a Detail read only?
Still, the OK button is missing on Invoices.

Thanks