After updating hummingbird this morning we noticed a few sites that have both Smart Crawl and Hummingbird active are showing 500 internal server errors on admin when both plugins are active. Disabling one will fix the problem.
This isn't exclusive to all site, for example on our multisite network some sites are okay when going to wp-admin and others show a 500 error. Frontend of all sites are okay.
Disabling either Hummingbird or SmartCrawl fixes issue.
Any help will be great, for now Hummingbird has to be disabled which is a shame.