Same issue here but appears to be a browser error?
In latest Chrome (70.0.3538.77): ERR_SPDY_PROTOCOL_ERRORERR_SPDY_PROTOCOL_ERROR
Failed to load resource: net::ERR_SPDY_PROTOCOL_ERROR:
wp-content/plugins/nextgen-gallery/products/photocrati_nextgen/modules/ngglegacy/admin/edit-thumbnail.php?id=199
Check out this post…
http://www.amember.com/forum/threads/wordpress-4-4-conflicts.21367/
Looks like you need to update aMember, then manually install the included WP aMember plugin.
Hope this helps.
