Prerequisites:

Mic permissions are enabled.
"Allow" or "Don't Allow" button from “Allow Firefox Voice to Collect Voice Transcriptions” pop-up is clicked.
Make a command before following the bellow steps, e.g. "Define voice".

STR:

1. Use the shortcut or click on the mic icon from the browser toolbar.
2. Say or write a "Timer" command, e.g. "Set timer for 20 seconds", "Timer for 10 seconds".
3. Click the sad emoticon from "Did we get this right" section.

Expected result:

The negative feedback display is shown in the doorhanger without issues.

Actual result:

Transcription of the command made from prerequisites is shown bellow "1 min ago you said" and not the transcription of the "Timer" command.

Notes:

Reproduced on Mac 10.14 with Firefox Nightly 76.0a1 (2020-03-26).
Negative feedback display might not be shown, like in #1387.