mpc500 clock out of time (master AND slave)

I've been trying to use my mpc500 to sequence some external midi gear, sending its internal clock to my other hardware sequencers...but it doesn't want to stay in sync.

I have tried the mpc500 as master...with elektron analog keys, rytm, roland tr8 slaved to its clock (using a kenton midi thru-5 to send the midi clock to everything)...but the mpc goes out of time after about 16 bars. The metronome is noticeably fast, and gets progressively worse over time. Within a minute the metronome is a full 16th early...and it keeps going more and more out of sync. Sounds pretty rubbish.

The strangest thing is that all the other gear stays in time with each other!! Seems like the mpc is sending the correct clock out, but it's own sequencer is drifting out of time with it's own internal clock!!! Weirdness.

I also tried the mpc as slave, with either of the elektron machines as master...again, the mpc goes out of time...metronome speeds up. Useless. The other gear stays in time perfectly with the elektron clock when setup like this.

Anyone had similar issues?

I've tried OS 1.11...1.13...1.30 and 1.31. Can anyone help me out here please?

Mine syncs without problems, both as master and slave, to either a computer or an Alesis hr16 .

Have you tried without the thru box? With different cables?

Are you sure you aren't creating some kind of midi loop? That can cause weirdness.