Last weekend I took the TG-UV2 out on a weekend road trip and exercised it a bit - periodic car to car traffic for 4 days. By and large it performed admirably, I didn't charge it all weekend and still had 2/3 indicated battery life upon returning home.
One problem I did encounter was transmitting on a hot day in the UHF band. For a while the transmitter was very finicky, when keyed with the PTT it would beep and display 'LOST' on the screen, not actually transmitting anything. The manual says "If PLL unlock, LCD displays LOST", so I surmise that when it's too warm the PLL's components drift and pull it off frequency. It's a bit weird that this only happens for transmit - RX was totally fine - but perhaps this transceiver uses dual PLLs to support split band/frequency RX/TX and for some reason the TX PLL is less stable with temperature or somehow gets loaded down by the TX stage. It's also worth nothing that VHF was totally fine during this period of failure on UHF.
Strange problem, I'm still quite happy with the radio but this was a tad frustrating while on the road.