This problem manifests itself in two ways: 1) Solr fields are not showing up for admnistrative users when they try to add a field to a View using the Views GUI and 2) when the view is executed (e.g. block or page is rendered to end user), Solr fields are dropped from the View resulting in a bad handler error message and in cases where the field is configured as sortable, a WSOD to the end user
Tricky thing is that both manifestations of the problem are intermittent and difficult to reproduce. But, I am not the only person to see them. Rosie Le Faive has also seen it happen and may be able to provide some additional detail that may help track down the issue.