The reason why technology has seemed always to progress is that, until perhaps a century or two before the Industrial Revolution, most technology was small-scale technology. But most of the technology developed since the Industrial Revolution is organization-dependent technology. Take the refrigerator for example. If by some miracle they did succeed in building one it would be useless to them without a reliable source of electric power. So they would have to dam a stream and build a generator.
Generators require large amounts of copper wire.
Imagine trying to make that wire without modern machinery. It would be much easier to build an icehouse or preserve food by drying or picking, as was done before the invention of the refrigerator. So it is clear that if the industrial system were once thoroughly broken down, refrigeration technology would quickly be lost. The same is true of other organization-dependent technology. Surviving technical books would be few and scattered.