--- res/res_rtp_asterisk.c.orig	2021-03-28 20:28:48.586296475 -0400
+++ res/res_rtp_asterisk.c	2021-03-29 09:58:21.375152082 -0400
@@ -5483,7 +5483,9 @@
 		instance, type == AST_FRAME_DTMF_END ? "END" : "BEGIN",
 		rtp->resp, rtp->resp,
 		ast_sockaddr_stringify(&remote_address));
-	if (rtp->resp == 'X') {
+	/* To avoid duplicate flash events, ignore flash end events:
+	dtmf_duration and dtmf_timeout are 0 for start, > 0 for end */
+	if (rtp->resp == 'X' && rtp->dtmf_duration == 0 && rtp->dtmf_timeout == 0) {
 		rtp->f.frametype = AST_FRAME_CONTROL;
 		rtp->f.subclass.integer = AST_CONTROL_FLASH;
 	} else {