I tried to work with my Backdrop site and see the strange order of the blocks on the page /admin/structure/block. By installing clean Backdrop CMS v. 1.20.0, I saw the same problem. In the screenshot I created four blocks for testing. First row - block 1, Second row - blocks 1 and 2, Third row - blocks 1, 2 and 3, etc...

v 1.19.4



I don't see anything strange or unexpected in this screenshot.

This is a normal view of page with created custom blocks.


After creating a custom block in order to see it in the design of your website you need to add it to the required layout - for example on a page for default layout:


Oh, now I see, the new blocks are arranged inline to the previous ones.

I confirm that this is also the case in one of my sites with Backdrop CMS 1.20.0 - without interfering with its normal operation with custom blocks.

I don't have this on another site that hasn't been updated and is still in version 1.19.3.