I found this one: https://wordpress.org/support/topic/javascript-error-on-pages-without-sharebar
The hack proposed in that topic solved my issue which was caused by JS error. Hoping that plugin will be fixed at some point, so I don’t need to hack into its code with every update…
I had something similar and my issue seems to be related to Sharebar plugin of WordPress. Disabling that plugin makes the toolbar buttons appear properly. Will research more what can be done w/o disabling it, the plugin itself is pretty nice besides this issue.