MG 2.3 Latest Media - filmstrip not appearing

[Mikethemix]

After upgrading our test site to 2.3, the filmstrip showing most recently added media no longer appears:

For comparison, this is how it looks on our live MG 2.2 site:

 

[Old Nick]

Your test site is a copy of your live site?

 

[Mikethemix]

Its is reduced data copy of the live site (to save space) - however it has all the functions of the live site and sufficient data to test functionality.
We always install updates first on the test site, check them out before doing the same to the live site.

 

[Old Nick]

Creating a new widget with the same parameter produces the same behaviour?

 

[Mikethemix]

Yes, normally everything works the same.
We have exactly the same add-ons on both sites, the same widgets too.
Before doing the 2.2 to 2.3 upgrade I updated all the add-ons to the latest releases and they were all working fine on the test site.
After doing the upgrade to 2.3, some of the add-ons did not work correctly and I have disabled them - they clearly need to be updated to 2.3.

However the specific issue of the film strip remains the same - ie not working.
There are other issues too - when hovering over the thumbnail of a media gallery photo, normally a small "selection" box appears - which allow moderation options to be selected. That is not working.

This is how it appears on the live site (when hovering over first thumbnail):



This is how it appears on the test site (when hovering)

 

[Old Nick]

Any outdated templates or some code in extra.less template that might interfere?



Normally the transparent blocks of info are not all displayed at the same time, but simply when hovering over each thumbnail, so there is a code that produces this.

 

[Mikethemix]

Good suggestions. Yes, we developed an add-on to show the blocks of info all the time on the live site. I have disabled that on the test site (that didn't work correctly either).
I will look into the extra.less template, thanks.
All things considered, I am wondering what is the benefit of 2.3 and whether its worth the effort.