Hi, New member, long time lurker.
I purchased my DX80 a few months ago. It had the 1.3.3 firmware version installed. Have tried a couple other firmwares, pleased with 1.5.8 so far.
As of a couple weeks ago I have noticed the battery draining issue some others here have discovered. I mostly play 24/96 files. And don't use the device more than a half hour at a time. Usually in my car, and also at home via USB. It will start out charged or 90% range, then it goes down 20-30 mins to 60% or thereabouts. I'd leave it off and use it on way home from work, from 60% when I get home (half hour of playing) it goes near dead or shuts off. I noticed when it goes to 60-70% and fit the charging cable from my car into it, it will rapidly charge. Reads that way anyway. Then take the charger cable out, it will discharge as usual again.
I read somewhere that you should take caution not to let the battery drain to 0% or you could possibly damage the battery. I'd imagine there are some safeguards factored into the firmware preventing the device from allowing it to go to 0%. Could this issue be involved in what seems to be an in-house battery defect, ie triggering the battery to go wonky? Just adding to the discussion. I'll be contacting support and ship it off to get a battery replacement asap.