https://github.com/espeak-ng/espeak-ng/issues/171
will be fixed by a506dc52416d4cb73372a63123d51cd2ea0f7209 in next release.

--- a/src/libespeak-ng/speech.c
+++ b/src/libespeak-ng/speech.c
@@ -79,6 +79,7 @@ int (*uri_callback)(int, const char *, c
 int (*phoneme_callback)(const char *) = NULL;
 
 char path_home[N_PATH_HOME]; // this is the espeak-ng-data directory
+static int didsave_parameters;
 extern int saved_parameters[N_SPEECH_PARAM]; // Parameters saved on synthesis start
 
 static int dispatch_audio(short *outbuf, int length, espeak_EVENT *event)
@@ -477,8 +478,11 @@ espeak_ng_STATUS sync_espeak_Synth(unsig
 	my_unique_identifier = unique_identifier;
 	my_user_data = user_data;
 
+	didsave_parameters = 1;
 	for (int i = 0; i < N_SPEECH_PARAM; i++)
+	{
 		saved_parameters[i] = param_stack[0].parameter[i];
+	}
 
 	switch (position_type)
 	{
@@ -816,8 +820,10 @@ ESPEAK_NG_API espeak_ng_STATUS espeak_ng
 #endif
 	embedded_value[EMBED_T] = 0; // reset echo for pronunciation announcements
 
+    if (didsave_parameters)
 	for (int i = 0; i < N_SPEECH_PARAM; i++)
 		SetParameter(i, saved_parameters[i], 0);
+    didsave_parameters = 0;
 
 	return ENS_OK;
 }
