Gallery in edit mode loads really slow any additional pictures

Hello,

I have two galleries that I display in my website here:

https://www.filmmining101.com/hall-of-fame/best-film-shots-of-all-time

https://www.filmmining101.com/hall-of-fame/most-beautiful-movie-shots-of-all-time

Yet when I am in edit mode and I want to upload more pictures, even if I put one more, it takes more than ten minutes to appear while those already displayed are empty boxes.

I can only presume that it might have something to do with the number of the pictures and that the gallery cannot handle it? I could be wrong.

If that is case, is there anyway around it? I suppose one straightforward way is to split the galleries (which I do not want to) into smaller blocks.

Any thoughts or insights about this, would be very much appreciated it!

G