diff --git a/mpvcore/command.c b/mpvcore/command.c
index 038e58bc8d..f16d171bf4 100644
--- a/mpvcore/command.c
+++ b/mpvcore/command.c
@@ -2502,6 +2502,11 @@ void run_command(MPContext *mpctx, mp_cmd_t *cmd)
                     set_osd_tmsg(mpctx, OSD_MSG_SUB_DELAY, osdl, osd_duration,
                                  "Sub delay: %d ms", ROUND(opts->sub_delay * 1000));
                 } else {
+                    // We can easily get stuck by failing to seek to the video
+                    // frame which actually shows the sub first (because video
+                    // frame PTS and sub PTS rarely match exactly). Add some
+                    // rounding for the mess of it.
+                    a[0] += 0.01 * (a[1] > 0 ? 1 : -1);
                     queue_seek(mpctx, MPSEEK_RELATIVE, a[0], 1);
                     set_osd_function(mpctx, (a[0] > 0) ? OSD_FFW : OSD_REW);
                     if (bar_osd)
diff --git a/sub/sd_ass.c b/sub/sd_ass.c
index 7de0ab6c43..591f9d5105 100644
--- a/sub/sd_ass.c
+++ b/sub/sd_ass.c
@@ -289,8 +289,11 @@ static int control(struct sd *sd, enum sd_ctrl cmd, void *arg)
     switch (cmd) {
     case SD_CTRL_SUB_STEP: {
         double *a = arg;
-        a[0] = ass_step_sub(ctx->ass_track, a[0] * 1000 + .5, a[1]) / 1000.0;
-        return CONTROL_OK;
+        long long res = ass_step_sub(ctx->ass_track, a[0] * 1000 + 0.5, a[1]);
+        if (!res)
+            return false;
+        a[0] = res / 1000.0;
+        return true;
     case SD_CTRL_SET_VIDEO_PARAMS:
         ctx->video_params = *(struct mp_image_params *)arg;
         return CONTROL_OK;