title: Cloud Composer throwing InvalidToken after adding another node
body: <p>I recently added a few new DAGs to production airflow and as a result decided to scale up the number of nodes in the Composer pool. After doing so I got the error: <code>Can't decrypt _val for key=&lt;KEY&gt;, invalid token or value</code>. This happens now for every single DAG that uses variables. It's not the same key either, it depends on what variables the DAG needs.</p>
  
  <p>I immediately scaled Composer back down to 3 nodes and the problem persisted.</p>
  
  <p>I have tried re-saving all of the Variables, recreating them in the UI (which says they are all valid), recreating them in the CLI (which lists <code>invalid</code> for every single one). </p>
  
  <p>I have also tried updating configuration to try and reboot the server, and manually stopping the VM instances.</p>
  
  <p>Composer also seems to negate the ability to update the Fernet Key, so I can't try and use a new one. For some reason it appears that the permanent one Composer has assigned is now invalid.</p>
  
  <p>Is there anything else that can be done to remedy that problem short of recreating the environment?</p>