Generated by XState Viz: https://xstate.js.org/viz/?gist=7711b52a5cb2e43e59d24b00e3c60b53

machine.js

  // Available variables:
  // - Machine
  // - interpret
  // - assign
  // - send
  // - sendParent
  // - spawn
  // - raise
  // - actions
  // - XState (all XState exports)
  
  const CHANGE = [
        {
          actions: ['log', 'storeCurrent']
        },
        {
          cond: 'isChanged',
          target: 'validating'
        },
        {target: 'unchanged'}
      ]
  
  const fieldMachine = Machine({
    id: 'fetch',
    initial: 'unchanged',
    context: {
      original: 'one',
      current: 'one'
    },
    states: {
      unchanged: {
        on: {CHANGE}
      },
      validating: {
        on: {
          CHANGE,
          VALID: 'submittable',
          INVALID: 'invalid'
        }
      },
      invalid: {
        on: {CHANGE}
      },
      submittable: {
        CHANGE,
        SUBMIT: {
          actions: 'save',
          target: 'unchanged'
        }
      },
    }
  },{
    actions:{
      log: console.error,
      storeCurrent: assign({current: (_, event) => event.value || ''
      }),
      save: assign({original: (c) => c.current})
    },
    guards:{
      isChanged: c => {
        console.log('isChanged', c)
        return c.current !== c.original
      }
    }
  });
  

This machine has several issues, the one I got stuck with (including many possible solutions):
statelyai/xstate#1565

The solution I picked and other fixes are in a second gist:
https://gist.github.com/karfau/760d85cb7ed38017a31f958fef883c7e