If I set Special:Preferences > Recent changes > "Number of edits to show in recent changes, page histories, and in logs, by default:" to 1000, clicking "older 50" (next page) button in User contributions on mobile will take me to next 1000 edits, but the number of edit displayed is still 50.
In the other words. Visit User contributions page will get recently 1~50 edits. Then clicking "older 50" button. You will get recently 1001~1050 edits.

Step:

1. Set Special:Preferences > Recent changes > "Number of edits to show in recent changes, page histories, and in logs, by default:" to 1000
2. Visit https://zh.m.wikipedia.org/wiki/Special:Contributions/Xiplus . You will get recently 1~50 edits.
3. Then click "older 50". You will get recently 1001~1050 edits.

I don't know how to clearly describe this problem. If you understand me, feel free to change the title and description.

Developer notes

Contributions page is a different page altogether and will only be fixed when it's not or if more development is pushed into the mobile versions of these pages.