Go to this infinite scrolling example, scroll down (at least to post 201), click at the column header "Last Post" to (remote) sort and watch the first column (post number). The view jumps always back to the first page with post #1, independent of the scroll bar state.

The fix for me was to insert the line

me.currentPage = page;

to the function "prefetchPage" in the file src/data/Store.js:

PHP Code:
    prefetchPage: function(pageoptions) {
        var 
me this,
            
pageSize me.pageSize,
            
start = (page 1) * me.pageSize,
            
end start pageSize;

        if (
Ext.Array.indexOf(me.pagesRequestedpage) === -&& !me.rangeSatisfied(startend)) {
            
options options || {};
            
me.currentPage page;
            
me.pagesRequested.push(page);
            
Ext.applyIf(options, {
                
page page,
                
startstart,
                
limitpageSize,
                
callbackme.onWaitForGuarantee,
                
scopeme
            
});

            
me.prefetch(options);
        }
    }, 
I don't know if this the right fix, but it works for me.