I came across a bug of the Yaesu FT-817 today that was previously unknown by many people. At least I didn't know about it. Another bug or shortcoming of the FT-817 was pointed out to me last year by PE1BVQ.
The first one is the blown finals caused by a flat battery problem. As you all know a battery will go flat after a while due to internal self discharge. If so the voltage will drop of course. At a certain point the PA which is directly connected to Vbatt goes into self oscillation and basically commits suicide. I guess this will not happen when the battery is new but when it is getting older or if you leave the radio off for a long time the danger is growing. Best solution is to remove the battery. If you use the battery often you better install a switch to disconnect the battery.
Update 22-Sept.: Steve G1KQH pointed me towards a glitch in the charging circuit. This can happen when the radio is fed with a quick on/off power supply like a broken supplycord. When you switch the radio on you don't have audio and display flashes. This is the solution found on G0FTD's site:
Insert some half charged batteries in the FT817 (so that the charger sense circuit knows that the batteries can be charged). Switch on the rig with a 13.8v PSU and follow the procedure to charge the internal batteries). This involves setting one menu to 6 hours time, and then on the 3 F-keys turning the charger on. Switch the rig off and the LED on the front panel glows orange.Allow the charge cycle to complete. Disconnect the rig PSU. Switch radio back on using the internal cells. Pull out one of the AA cells to make it look like the battery has depleted it's voltage.Now plug the rig back on to the main 13.8v PSU and switch the rig back on.
If anyone knows more bugs I'm happy to publish them here for future reference!