<Space>sm not working

[pebbe]

I did a fresh install with this repro. I have a problem with shortcuts that begin with s.

First I run :split. Then I want to maximize one window with sm. That doesn't work. Instead, after typing s there is a short delay, then the cursor moves one position to the right, the character under the cursor is removed, and neovim switches to insert mode. What is going on here?

I run :map to see all mappings. It lists <Space>sm, but no s .

Tested with NVIM v0.9.0-dev-530+gde90a8bfe and NVIM v0.8.1

[pebbe]

When I'm really fast, it works. I sligt delay after 's' results in that strange behavior.