USE_ESPEAK_FALLBACK doesn't work

[sl5net]

The following configuration does not produce any sound,
when piper is not running.

USE_AS_PRIMARY_SPEAK = "piper"
# USE_AS_PRIMARY_SPEAK = "ESPEAK"
USE_ESPEAK_FALLBACK = True
ESPEAK_FALLBACK_AMPLITUDE = 80

The simple quick fix in just a few seconds is as follows.

# USE_AS_PRIMARY_SPEAK = "piper"
USE_AS_PRIMARY_SPEAK = "ESPEAK"
USE_ESPEAK_FALLBACK = True
ESPEAK_FALLBACK_AMPLITUDE = 80

probably also woks (not pretty coding):

USE_AS_PRIMARY_SPEAK = "piper"
USE_AS_PRIMARY_SPEAK = "ESPEAK"
USE_ESPEAK_FALLBACK = True
ESPEAK_FALLBACK_AMPLITUDE = 80

version:

v0.31.00