SORTING more than 1000 files by FIRST TAG

I have more than 1000 files (about 1200). Search is set to 3000, and display to 1000 (max allowed). Sorting is set to ‘FIRST TAG’. The FIRST TAG is: ‘number’-‘three letter topic description for that number’- ‘date of birth of author’ - author’s name, eg: ’ 35-eng-1812-Dickens_Charles_John_Huffam’. All files have the tag ‘book’ as LAST TAG. Tags are stored on the file names. System: Ubuntu 22.04 native. Tagspaces 5.6.2.
Problem: Search for ‘book’ produces 2 (two) pages. The first page is correctly sorted. When I move to the second page I have the right sorting for 2/3 seconds, then everything is mixed on both pages.
I have tried several settings (500/100 files display, grid and list perspective). Nothing works.

Solved with the last version 5.7.5 on Linux/Ubuntu.