Hi @thendb,
Thank you for your reply.
I have tested it on my test site using latest version of Custom Sidebars & WooCommerce plugins and the custom sidebar worked fine without any issue on woocommerce pages (cart/checkout/etc) as displayed in the following screenshots.
https://i.imgur.com/z1r5ehD.png
https://i.imgur.com/sEFAo93.png
https://i.imgur.com/zQ7p5b3.png
Make sure you are using latest versions of all plugins and share me the screenshots of it as i have shared you so that i can troubleshoot it.
For screenshots, you can simply provide a link to an image through Google Drive, Dropbox, screencast.com, https://imgur.com/ or other image service. ??
Also if you can please share URL of the page.
This can also be due to plugin/theme conflict.
To find find out plugin/theme conflict you can just try on your development site using default WordPress theme like Twenty Thirteen and deactivating all other plugins as displayed in the following flowchart to know which theme/plugin is conflicting if any.
https://premium.wpmudev.org/wp-content/uploads/2013/12/Support-Process-Support-Process.png
Regards,
Vinod Dalvi