A long time ago, maybe 2016?, There were some community members who Attempted to implement double tap for switches which didn’t provide that feature in their own firmware. They would capture the tap and then try to do the timing until the next tap.
This had a lot of issues, particularly cloud latency throwing off the timer, but it did work for some people some times with some switches.
However, it depended on being able to distinguish between a physical tap on the switch and a network command, or otherwise a lot of things would be perceived as double taps which were not.
And that distinction relied on a value called “isphysical“ for Zwave switches.
The problem is that “isphysical“ is implemented differently by different device manufacturers, and in particular, some repeating devices cause the “isphysical“ to be changed to the equivalent “is network“ When they pass along a message they received from another device.
So that meant that sometimes the double tap capture would fail just because the message had gone through a different repeater on its way to the hub.
This situation caused a lot of frustration for many people, and ultimately, again I think back in 2017, smartthings made the decision that they would no longer support the “isphysical“ value at all in the stock DTHs. Meaning you could no longer use it in a smart app. It meant people lost the ability to write a rule for a custom based double tap for a device which did not itself provide that feature, but at least everything worked the same for everyone.
So there were some people who had a custom double tap smart app working back in, say, 2015 who then lost that feature a couple years later, I don’t know if that’s what happened to you, but your switches are old enough that it might be. You could get it back by using a custom DTH, but then the switch wouldn’t run local and that in turn introduced additional cloud latency. 
Here’s a comment from a staff engineer back in the day:
There are a number of models available now which to provide a double tap feature in the switch itself, so most people who want that just get those.