DVL models are extremely prone to various error codes showing up for no apparent reason, however the e-04 indicates that there is a problem with feedback from the video drum and this sometimes being purely because the video heads require cleaning, but if as you say that you have already tried cleaning the video heads (cleaning cassette or liquid?) it doesnt really leave you with many options, that is without partial dismantling of the casing to enable checking of the drum ribbon cable to PCB connector, which can be one possible source of the problem. In saying that though, DVL models do frequently display some very misleading spurious error code numbers that are not really 100% applicable to the actual reason for the fault, this happening because the mechanism has various operating position sensing switches etc, and if the mechanism isn't quite locked into a particular position after a loading / unloading operation a safeguard fault condition can spring up, this being the likely reason why many report that firmly tapping (or other more violent measures!) the sides of the case can sometimes make the device start operating again, the action having jolted the mechanism into activating a sensor. There is a wealth of suggested remedies, but unfortunately too numerous to paste into a web page, and it should also be said that its very advisable that only someone acquaint at working with small precision pieces of equipment should attempt to do any work within the camcorder casing, as the device could well end up a write off.