I've found conflict between SmartCrawl and Nitro Toolkit. When both plugin are active it's not possible to save meta title (and other meta tags). To replicate, go edit the homepage, change the meta title and save the post, you will see that the data is not stored and also that the provided meta title is also weird.
I manage to find the issue, this is related with a visual composer element that is made from the theme editor, they get a list of all products and populate a field and somehow populate also the fields from Smartcrawl. I will check with their support, but could you look from your end too?
It is in the file products.php I think ()