That part about reflashing is exactly the point -- since I don't own a DSO, I have no idea what's involved if reflashing were needed (assuming, for example, with the Rigol DS1054Z).
I've not done it on a Rigol, and I didn't see anything in the User Guide (262pg .pdf manual, not the thin Quick Start Guide they actually print). But I'd expect you'd be able to do it over the USB port, as that's how you update it to newer firmware (may not have written the software to downgrade firmware revisions yet). IIRC, I've read about other members being able to start their scope on a USB stick when there was a problem (insert USB stick prior to boot, then power it up).
There's also SCPI commands (commands can be found
here). Physical interfaces are USB and LAN, and the manual has a section on GPIB as well. Past that, it's going to require special tools (programmer; either over JTAG pins/landings or desoldering and using an adapter board).
Not investigated this thoroughly yet, so I don't know of any precise procedure (especially any that doesn't involve a programmer).
Personally, I think I'm just going to wait until Rigol solves it in an official release (there is currently a Beta release, but there are issues with it).
Just in case you're not aware though, it's a nice little scope overall, and
is certainly usable in it's current state. So it's not an "OMG, this thing is a useless pile of junk" situation by any means. The EEVBlog community is just good at finding bugs, and making threads about them (helps get the manufacturer's attention, so a big
IMHO).