Slideshow / Tiled Gallery block: block controls alignment issues

For some reason, the slideshow toolbar is aligned to the complete left of the editor, while core blocks' controls appear right above the block. Here is a comparison:

https://user-images.githubusercontent.com/426388/109131218-e0f35880-7752-11eb-89f9-ea49af4a1c70.mov

p8oabR-Co-p2h#comment-4999

The issue names the Slideshow and Tiled Gallery blocks and provides a comparison video, but no file, test, or entry point. Locate their editor controls, reproduce the alignment difference against a core block, and verify that the toolbar appears above its block rather than at the editor's left edge.

Written by the indexing model from the issue text.