Hi @Syamsg. Thank you for your report.
To speed up processing of this issue, make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce.

• For more details, review the Magento Contributor Assistant documentation.
• Add a comment to assign the issue: @magento I am working on this
• To learn more about issue processing workflow, refer to the Code Contributions.

Join Magento Community Engineering Slack and ask your questions in #github channel.
⚠️ According to the Magento Contribution requirements, all issues must go through the Community Contributions Triage process. Community Contributions Triage is a public meeting.
🕙 You can find the schedule on the Magento Community Calendar page.
📞 The triage of issues happens in the queue order. If you want to speed up the delivery of your contribution, join the Community Contributions Triage session to discuss the appropriate ticket.

Hi @engcom-November. Thank you for working on this issue.
In order to make sure that issue has enough information and ready for development, please read and check the following instruction: 👇

• 1. Verify that issue has all the required information. (Preconditions, Steps to reproduce, Expected result, Actual result).

  2. Verify that issue has a meaningful description and provides enough information to reproduce the issue.

  3. Add Area: XXXXX label to the ticket, indicating the functional areas it may be related to.

  4. Verify that the issue is reproducible on 2.4-develop branch

  Details

  - If the issue is reproducible on 2.4-develop branch, please, add the label Reproduced on 2.4.x.
  - If the issue is not reproducible, add your comment that issue is not reproducible and close the issue and stop verification process here!

  5. Add label Issue: Confirmed once verification is complete.

  6. Make sure that automatic system confirms that report has been added to the backlog.
  To pick up a draggable item, press the space bar. While dragging, use the arrow keys to move the item. Press space again to drop the item in its new position, or press escape to cancel.

Hello @Syamsg ,

Thank you for your report and collaboration.

We attempted to reproduce the issue in the latest 2.4-develop instance. We are able to reproduce the issue. Please refer to the attached screenshot for details.

Steps to Reproduce:

• Authenticate as that customer and obtain a valid bearer token.
• Send this GraphQL mutation:

mutation {
  updateProductsInWishlist(
    wishlistId: "1",
    wishlistItems: [
      {
        wishlist_item_id: "1",
        quantity: 2,
        description: ""
      }
    ]
  ) {
    wishlist {
      id
      items {
        id
        description
        product { name }
      }
    }
  }
}

We followed the preconditions and steps as provided and encountered the issue.

Therefore, we are marking this ticket as "Issue: Confirmed."

Thank you!

✅ Jira issue https://jira.corp.adobe.com/browse/AC-14682 is successfully created for this GitHub issue.

✅ Confirmed by @engcom-November. Thank you for verifying the issue.
Issue Available: @engcom-November, You will be automatically unassigned. Contributors/Maintainers can claim this issue to continue. To reclaim and continue work, reassign the ticket to yourself.

@engcom-November @Syamsg
I checked this issue, and in my opinion, the problem is with the wishlist_item_id parameter.

Screenshot from comment:#39911 (comment)

In the request, wishlist_item_id: "1", but in the response, wishlist_item_id: "5".

In this situation, we don't have $wishlistItemToUpdate in:
\Magento\WishlistGraphQl\Model\Resolver\UpdateProductsInWishlist::resolve
\Magento\WishlistGraphQl\Model\UpdateWishlistItem::execute

However, if we set an existing wishlist_item_id (from the wishlist_item table):

Everything looks OK. Please correct me if I misunderstood something.

Hello @Syamsg ,

Could you please follow the steps provided above and let us know if the issue still persists?

Thank you!