Ng-click does not work reliably on android tablet

I use habpanel on my android tablet with the keypad widget by Murpher.

Sometimes the buttons do not work and I have to click multiple times on a single button until the click has been processed. You can see in the UI that the button has not been pressed when lifting the finger, so I guess it has nothing to do with what is happening inside the ng-click, but seems to be a problem of either habpanel/angular/whatever library.

Everything works as expected when used from the desktop.

Has somebody else seen this and knows how to fix it?

Just for completeness, here is the code that I use:

    <div class="widget" ng-form="myKeyPad" ng-init="myCode=''">
      <label class="mask">&nbsp;{{ "**************" |limitTo:myCode.length }}&nbsp;</label>
     
      <table width="97%">
        <tr align="center">
          <td width="33%"><button ng-click="myCode= myCode + 1" class="numberButton">1</button></td>
          <td width="33%"><button ng-click="myCode= myCode + 2" class="numberButton">2</button></td>
          <td width="33%"><button ng-click="myCode= myCode + 3" class="numberButton">3</button></td>
        </tr>
        <tr align="center">
          <td><button ng-click="myCode= myCode + 4" class="numberButton">4</button></td>
          <td><button ng-click="myCode= myCode + 5" class="numberButton">5</button></td>
          <td><button ng-click="myCode= myCode + 6" class="numberButton">6</button></td>
        </tr>
        <tr align="center">
          <td><button ng-click="myCode= myCode + 7" class="numberButton">7</button></td>
          <td><button ng-click="myCode= myCode + 8" class="numberButton">8</button></td>
          <td><button ng-click="myCode= myCode + 9" class="numberButton">9</button></td>
        </tr>
        <tr align="center">
          <td><button ng-class="{disabled: myCode.length == 0}" ng-click="myCode=''" class="textButton">Löschen</button></td>
          <td><button ng-click="myCode= myCode + 0" class="numberButton">0</button></td>
          <td><button ng-class="{disabled: myCode.length != config.code_length && config.code_length > 0}" ng-click="sendCmd(config.entered_value, myCode);myCode=''" class="textButton">Eingabe</button></td>
        </tr>
      </table>
      <hr class="separator"/>
      <table width="97%">
        <tr align="center">
          <td><div ng-click="sendCmd(config.alarm_cmd, 'INTERN')" class="activationButton">Intern</div></td>
          <td colspan="2"><div ng-click="sendCmd(config.alarm_cmd, 'EXTERN')" class="activationButton">Extern</div></td>
        </tr>
      </table>
    </div>

Thanks,
Volker