Gallery size limit? Galleries being limited to only 500ish photos and 5 pages

I’m in need of some help,

I have been using NEXTgen Pro for about 2 years now, I have come across a new issue where when posting a gallery with hundreds of photos (Photographer who takes long photoshoots for clients) where galleries are limiting themselves to only a few pages in thumbnail mode. Issue recently came up with a photoshoot involving 862 photos.

Inserted the gallery on the page to display 102 photos at a time but when looking at the pages marker bellow it only states 5 pages are available to view. If I adjust the photos per page the number will increase or decrease but the photos available for view are the same. It cuts of partially. Why is this? If I force type in the url I can view the further pages. If I use AJAX it however does not solve the problem.

Any advice as to why this is happening or solve it? If I split the gallery in two with half the photos in one gallery and half into another and post both on the same page all the photos will load BUT same situation where only the first few hundred will load into the gallery for view