Failed to construct 'Notification': Illegal constructor

[hosna]

@bletch

Can I ask what non-Discourse plugins you have installed? Let’s see if we can find some common potential cause outside of core.

I have two discourse forums. This error appears in both. However in one of them I have hundreds of these errors per hour and I think if its because of a plugin, its because of who is online plugin, which is not installed in the other forum.