Hello,
Thank you for using our theme and take our apologies if you faced any inconvenience.
1) Could you, please, provide us with 1 video how the mentioned plugins work with the default theme and 2d video how it works with the XStore? We need to check that to understand the issue. You can use Recordit tool to create and share video.
2) Provide us with WP Dashboard and FTP access to your site to allow us to fix issue after watching your videos.
3) There is no need to switch to the parent theme just to update it. You can continue using the child theme and just follow the docs https://xstore.helpscoutdocs.com/article/63-theme-update
If your developer made customization correctly you should not face any issues or lose any changes after the parent theme update. Anyway, do the files and DB backup before any update.
Regards