Broken deploy icon

Sometimes the deploy icon changes to a jagged/broken version as above. Nodes don't behave properly when this happens- configuration data et al disappears. This fixes itself on node-red restart. Could someone from the node-red team please tell me why I get this icon and what I can do to prevent this?

  1. what platform is NR running on?
  2. what OS and release?
  3. what version of NR and node.js?
  4. what browser are you using?
  5. does it happen with other browsers?
  6. what platform are you running the browser on?