ios – Firebase Firestore Swift – Pagination navigation backwards reveals improper objects

I am implementing pagination in my iOS Swift app with Firebase Firestore, and I am having points with backwards navigation. When clicking the “earlier web page” button, it reveals newer objects as a substitute of older ones.

This is my present implementation:

func loadNextPage() {
    guard let lastDocument = lastDocument else { return }
    
    isLoading = true
    currentPage += 1
    
    var question = db.assortment("objects")
        .order(by: "timestamp", descending: true)
        .begin(afterDocument: lastDocument)
        .restrict(to: itemsPerPage)
    
    // Apply filters...
    
    question.getDocuments { [weak self] snapshot, error in
        // Deal with outcomes...
        self.objects = snapshot.paperwork.compactMap { self.documentToItem($0) }
        self.lastDocument = snapshot.paperwork.final
    }
}

func loadPreviousPage() {
    guard !isLoading else { return }
    
    isLoading = true
    currentPage -= 1
    
    var question = db.assortment("objects")
        .order(by: "timestamp", descending: true)
    
    if let firstItem = objects.first {
        question = question.whereField("timestamp", isGreaterThan: firstItem.timestamp)
            .restrict(to: itemsPerPage)
    }
    
    // Apply filters...
    
    question.getDocuments { [weak self] snapshot, error in
        // Deal with outcomes...
        self.objects = snapshot.paperwork.compactMap { self.documentToItem($0) }
        self.lastDocument = snapshot.paperwork.final
    }
}

What I’ve tried thus far:

• Utilizing begin(after:) with the primary merchandise’s timestamp:
  swift

  question = question.begin(after: [firstItem.timestamp])
  

• Utilizing finish(earlier than:) with the primary merchandise’s timestamp:

  question = question.finish(earlier than: [firstItem.timestamp])
  

• Altering the order path for earlier web page:

  question = db.assortment("objects")
    .order(by: "timestamp", descending: false)
  

• Utilizing whereField with totally different comparisons:
  swift

  question = question.whereField("timestamp", isLessThan: firstItem.timestamp)
  

The pagination works completely when going ahead, however when attempting to go backwards:

• Typically it reveals the identical objects as the subsequent web page
• Typically it jumps to the primary web page
• Typically it reveals newer objects as a substitute of older ones

My knowledge construction in Firestore:

Assortment with paperwork
Every doc has a timestamp area (server timestamp)
Utilizing descending order by timestamp
Limiting to N objects per web page

How can I implement correct backwards pagination that reveals the earlier N objects chronologically?