Oh fer goddsakes!
Look, quick history Redux:
2002: Some guys in Japan insist on designing the MPC4000/Z4/Z8 OS themselves and not using the team who did the OS for Akai's S5000/6000 sampler series. They also write the user guides in Japanese and have them translated into English by robots.
These Japs are not musicians, have never really used samplers or MPCs in anger, they're just engineers.
The result is a dry as dust user manual and an OS that is so full of bugs and unfinished half-ass-implemented features that it drives the power users who have forked out about £2500 on the thing nuts. SysEx is knackered. Track mutes are knackered. It's got 4 MIDI outs but you can only sent MIDI clock to one at a time. FX returns are 12dB quieter than the main bus. Gain architecture is all over the place. Can't save onto the inbuilt CD-ROM. You need to spend about £750 more to get the SPDIF, ADAT and 8-outs boards. And 512MB RAM..... this mothfckker ain't cheap and it's a pile of junk.
With customers in uproar, Akai UK finally get to wrest the thing away from Japan, and their developers, who have been behind Akai industry-standard samplers for years, start issuing OS updates to fix all this crap....
...BUT - some ass-clowns in Akai US start advertising all these bogus "forthcoming feautres" like record audio to CD, intellisampling, stream audio from hard drive, etc etc etc.
None of these were ever planned, some are impossible to implement on the hardware.
Units get sold in the US under the premise that MPC4000 will do all this fantasy stuff - sh*t really starts hitting fan - big time annoyed customers - Akai UK's remedial bug fix schedule torn to shreds by having to try and delivery all these promised features....
....result: Akai US goes banktrupt

(2003?)
Customer dissatisfaction high, Akai's fortunes teetering..... we get a few more OS updates from them but their heart's not in it and finally Akai UK/Japan goes bust too. (early 2005, was that?)
Akai bought by Numark,
MPC4000 never really supported since.
Numark bring out kiddie's toy versions of MPCs instead.
That's more or less it.
Basically MPC4000 shoulda been supa-killer top-of-the-range dream machine, ends up being a never-quite-finished white elephant, falling way short of its real potential.