Definitely seems like cache issue with the record for express-session.
try sudo npm cache clean? After that try manually clearing the cache files?
Search 500 errors here.
In a strange twist of fate, I tried searching to see if someone had reported that the search wasn't working, but the search wasn't working. Reloads the page you were on rather than going to the results. Trying to load the search directly offers a 500 error.
Should be fixed now. Updated the solr plugin to latest.