Sorting subpages after greater than 9

Hi, currently I have the problem that my order gets screwed up after more than 9 visible pages.
The tenth page will be sorted as number 2 whenever I switch another page to visible. The only way to fix this right now is to manually sort it in the content folder by adding the numbers by hand.

I tried

     sort: sort

in the parent blueprint but this causes a fatal error on my server (Allowed memory size of 134217728 bytes exhausted)

Any suggestions on how to fix this?

This has already been posted here: Kirby 2.5.9 Panel Page Re-Ordering Broken