Enterprise Alert using the Unified Communications Managed API of Microsoft for its Skype for Business / Lync module. We recently experienced some misbehavior and crashes here. Therefore, we highly recommend installing the following Microsoft hotfix if you use Enterprise Alert in conjunction with Skype for Business or Lync.
Unified Communications Managed API 2.0 Redist (64 Bit) Hotfix KB 2647091
After installing this hotfix, please check for additional Windows updates and install those as well. This will make sure your Skype for Business / Lync module can work properly.