Filter Icon for Activities on Social Pane missing

Hi everyone,

I'm having an issue that the filter button in the activities tab of the social pane has no icon. This is true for all entities.

The button works, I can filter the records, but it looks like this:

After clicking the button, it usually (but not always) looks like this:

So I have two questions:

1. Is this a known issue and if so, will there be a fix?
2. Is there any way I can fix this myself, so the correct filter button is displayed? Or, if this is not possible, can I just hide the button?

Thanks and kind regards,

Alex