action button not working

[dave-lawrence-dev]

jquery-confirm version:
v3.3.4

I'm submitting a ... (check one with "x")
[ x ] bug report
[ ] feature request
[ ] support request

Current behavior:
Very occasionally the 'SET' button in our dialog box is unresponsive and the action() is not called. the 'CANCEL' button works

Expected behavior:
SET should always work

Steps to reproduce:
This is a bug report from a customer, we have been unable to reproduce the fault in the office.

Related code:

$.confirm({
  theme: 'black',
  title: null,
  content: `<span style="font-size: 150%">Set state for ${item} to ${state}</span>`,
  buttons: {
    cancel: {
      text: "Cancel"
    },
    set : {
      text: `Set to '${state}'`,
      action: function() {
        console.log("Setting ${state}");
      }
    }
  }
});

I've had to redact this code from the original, so please excuse any typos.
Other information:
This is very rare; I've not seen the problem first hand.
I've replaced the actual code with a console.log()
The 'mouseover' effect for the SET button appears, but clicking just does nothing. no code is called. dialog remains open.