`(command &)` from .zshrc not executed until shell closed

**Describe the bug**

My .zshrc contains lines that call python scripts:

```
function f() {
(command python /path/to/app.py > dev/null 2>&1 &)
}
```
(The bug also happens with something simple like `(command notify-send foo &)`)

These run perfectly fine in Konsole and Kitty. But from Guake shells they are not executed until the shell is closed, or I open another tab. The rest of the .zshrc executes fine.

For example:

Every time a shell is opened, or a condition is met, command X should run. Instead:

1. Open fresh Guake
2. (X should run on start or when condition is met, but doesn't)
3. Open new tab in Guake
4. X runs
5. Close tab
6. Close last tab
7. X runs (too late)

**Expected behavior**

As soon as my lines are reached in .zshrc, or when they are trigged, for them to be executed.

**Actual behavior**

`command` not being executed until the shell is closed.

**To Reproduce**

Add `(command notify-send foo &)` to `.zshrc`
-------------------------------------------------------------------------------
$ guake --support

Guake Version: 3.10

Vte Version: 0.74.0

Vte Runtime Version: 0.74.0

--------------------------------------------------
GTK+ Version: 3.24.38

GDK Backend: