This is a long-standing issue on mobile; the only workaround I know of is to use << to go to the first page in the thread so that infinite scroll has nowhere to go.

It creates a poor user experience, because many long-running threads have useful knowledge/wisdom/etc. that has been distilled into a wiki to make it easy for newcomers to quickly orient themselves or learn the high points of whatever the topic is, but since people are frequently on mobile devices these days, it seems like many newer FTers have no ideas wikis even exist (much less how to defeat the infinite scroll problem), and consequently threads get filled with the same repetitive questions being asked over and over again.