The IRLP UHF repeater on 439.775 (IRLP node 6990) locked on transmit in the early hours of this morning, and so it has been powered down pending further investigation.
Seems to be operating normally after powering back up. So whatever it was is an intermittent latch up. Last time this happened like this it was a bad FET in the IRLP node controller. Maybe it's the same again?