As far as I see the losses, the minimum seems to be in epoch18 with 5167.
Even though the loss was a bit shaky before that, the min loss was still lowered before the patience was satisfied. After epoch 18 you would have to stay over 5167 for the next 10 epochs.
If you want to change this behavior, you could also play around with cooldown:

cooldown ( int  8) – Number of epochs to wait before resuming normal operation after lr has been reduced. Default: 0.