Try This
 

I like to use 2- 3 maybe 4 arps in multi mode playing i note loops etc,,
and im sure im not alone so to help fellow user Please try the following and hopefully access will sort this out

Try this
Multi mode
Midi channel 1 load up Rom M 51 no unison
Midi channel 2 load up Rom A 4 again take of unison
Now write in a 3 note chord sustaned over a 2 bar loop with M51
Next switch to mid channel 2 and play the same chord or other 3 note chords over the loop
The arp from M51 will not now warp in and out of time everytime
This is just 1 example