If a bunch of people ask for refunds, it probably won't do that much damage.
These pre-orders are on Heighway's books as liabilities. To write off the liability for each individual order, Heighway must either deliver a pinball machine or a refund. It's going to cost Heighway a bunch of money either way. Delivering a machine should cost less than providing a refund so, to Heighway, the true cost of providing a refund is only the profit on that order, which will be lost. Supposedly, there isn't much profit in the current situation, so it shouldn't make that much of a difference.
The investors know the status of the balance sheets, and what must be done to deliver against the liabilities, before they can even think about building machines for profit.
I'm not terribly worried, but I only have a downpayment at stake. Staying in for now.