ttb-direction for Thumbnails - perPage doesn't work

[Shau1a]

Hello!
Great slider, thank you for your work!

Nevertheless I have updated my slider to the version 3.1.3 and catch a problem with ttb thumbnail slider.
'perPage' option seems not working. I have a height for the slider like 300px and fixedHeight which is set in slider options for the each slide like 125px, so I try to set 'perPage' option like 2 to avoid big white space in the bottom after reaching the last slide, but still get it.
Would be very grateful to get advise or fix!

[NaotoshiFujita]

Splide with fixedHeight ignores perPage.
https://splidejs.com/guides/options/#fixedwidth

This example will help you:
https://codesandbox.io/s/thumbnails-ziyse