Function generator: small frequency difference between DCP and MIO168 module

[fietser28]

With the following settings in function generator:

DCP#2, DOUT1, AOUT1 all to pulse, 200ms period, 50ms pulse width:

When I turn the output on, this is shown (single trigger on turn-on):

They all trigger at the same time as expected, duration of DCP is slightly below 50ms.
The next few triggers I see some jitter between the pulses.

If I keep the output running and wait a bit, I can see the DCP and MIO pulses shift in time the MIO pulse gets ahead of the DCP pulse. After 60 sec, it looks like:

And after 210 sec:

Sometimes there also is a small jump.

Running 1.8-alpha2 and 0.12 on MIO168.