Set gst caps field

Hi! I am having a hard time trying to set a field in a GstCaps of mine. My code below does not seem to update "framerate" during runtime.

GstCaps *capture_format_caps = gst_caps_new_simple("video/x-raw",
                                        "width", G_TYPE_INT, size.width,
                                        "height", G_TYPE_INT, size.height,
                                        "framerate", GST_TYPE_FRACTION, framerate.numerator, framerate.denominator,
                                        nullptr);
assert(capture_format_caps);
if(format != "")
    gst_caps_set_simple(capture_format_caps, 
                        "format", G_TYPE_STRING, format.c_str(), 
                        nullptr);

g_object_set(G_OBJECT(capturecapsfilter_), "caps", capture_format_caps, nullptr);
gst_caps_unref(capture_format_caps);

// later on in the code ...

capture_format_caps = gst_caps_copy(capture_format_caps);
gst_caps_set_simple(capture_format_caps,
                    "framerate", GST_TYPE_FRACTION, framerate.numerator, framerate.denominator,
                    nullptr);
gst_caps_unref(capture_format_caps);