Filter by issue

Recently I updated my Sampression Lite theme to 1.5.1 (yup, only recently ?? ), and after that the filter on the front page started behaving strangely. It showed all the posts by default, but when I clicked on any other option (category), it did not show anything at all.

My first idea was that I messed up something in my child theme, so I switched to parent Sampression Lite, but the problem stayed there as well. On further investigation I found out that some of the posts get shown. It seems like the filter works only for first page – e.g. filters only the first page, but ignores older posts.

My site is https://girl-gift.ru

Any help regarding this problem as well as any ideas where to search for answers is highly appreciated. I really love using Sampression Lite, and I would like to resolve this issue ??