Не разбираюсь в MPD, но полагаю что явно нужно указать тайм-аут для LCP-пингов:
set link keep-alive seconds max
This command enables the sending of LCP echo packets on the link. The first echo packet is sent after seconds seconds of quiet time (i.e., no frames received from the peer on that link). After seconds more seconds, another echo request is sent. If after max seconds of doing this no echo reply has been received yet, the link is brought down.
If seconds is zero, echo packets are disabled. The default values are five second intervals with a maximum no-reply time of fourty.
Скорее всего раньше это было неявно указано в MPD, а теперь по умолчанию выключено.
Например для пингов раз в 30 сек и отключения по неактивности через 1.5 минуты:
set link-keepalive 30 90