I had the same thing happen. Refreshed the page and the button to update was gone.

Pat and Jason,
Do you see that issue when you try to edit any theme?

Jason,
Are you using a custom or standard theme on the calendar page? If a custom theme what was its base theme (so I can report this issue)?

In the meantime, you can add this as a CSS resource on your page to adjust the color of the filters on hover (it will also affect the view picker on the calendar):

.nx-editor-header .nx-actionselect :hover { color:black; /*color of the text on the filters*/ background-color:gray;}

If this affects other buttons and / or filters on your page you can add a specific class to your calendar and to the CSS resource to only affect the calendar.

Thanks!

It’s not for editing a theme. I’m working with the standard themes.

I tested theme updating on 8.5.18 and 9.5.3. I’m 99% certain it’s specific to 9.5.4.

It this is the case, can you please add this as a known issue to the release.

PS: I have video proof, just not related to this.

Custom Theme in my case.  But the problem exists for the standard Lightning Theme - look at the Calendar filters on hover.  

The proposed CSS approach doesn’t really work.  I don’t want to override the background and text of the dropdown items themselves - those are fine, it’s just when you hover over the nx-actionselect nx-viewswitcher that it disappears from view (everything disappears except for the down arrow icon). 

Jason,
I’ll notify the developers of this issue in the Lightning theme and we’ll let you know when it’s fixed in a future release. Looks like I spoke too soon about the CSS, it does affect everything in the dropdown as well. Unfortunately, I think it’d be kind of complex to get it to only affect the top label (or at least it’s beyond me to figure out, sorry!)

Pat,
I’ll also let them know about the theme updating issue and we’ll let you know when that’s fixed, as well

Thanks guys!