Just received a Sandisk Ultra 64gb micro sdxc card. I formatted it with Fat32 and seems to be fine. The DX50 scans it and begins playing fine, but after 20 secs. or so it moves forward to the next track over and over. It plays fine in the Fiio x3. Turned off gapless on the DX50, no luck. Reformatted and reloaded the card to no avail. If I copy the files to one of my 128gb sdxc full size cards it plays the tracks fine. Any ideas why? Would hate not to be able to use this card with the IBasso. Other than this blip I am very happy with the DX50, have had the Fiio x3 for 2 weeks now and while it is a great Dap, I prefer the DX50's sq hands down. Wish the touchscreen was not so sensitive though.
Always worth checking the card - I had a duff one [Sandisk ultra 64gb] which formatted OK and worked fine on a colorfly C3 but caused problems on my DX50. I use h2testw on a windows PC to test my cards.