What is so problematic about the homophones 预订 and 预定 when negotiating contracts?
Usually, 预订 followed by a noun (object);  预定 followed by a verb (action). It is not difficult to tell the two apart.
Example:
预定明天出發 - scheduled to leave tomorrow
预订一打玫瑰 - place an order for a dozen roses
However, let's say you tell a supplier that &quot;想向你們预订 X number of Y&quot; (want to order X number of Y from you), and they agreed and said, &quot;會预定提供 X number of Y 給你&quot; (will schedule to provide X number of Y for you). If they can't deliver on the agreed date, they can argue: 'to schedule to' is the same as 'to prepare to'. It never was a firm order.

预订明天交貨 = ordered (goods), deliver tomorrow (a firm order)

预定明天交貨 = scheduled to deliver tomorrow (not a firm order)


预订 is an official contract. You are expected to pay for the goods and they are expected to deliver the goods
预定 is a 'promise to reserve', that's why we say 向餐館预定一张桌子 (Reserve a table from a restaurant) and say 向傢具店预订一张桌子 (pre-order a table from a furniture store)