Rasp 3 + Digi+ over Toslink plays music too fast

Dear forum,

I started a small projekt with my car-hifi, being fed up with changing CDs …
I wanted to feed a DSP (Match 82 pp, … 6…192 kHz automatic sample rate, 56 bit soundprozzi) with FLAC data over a raspberry 3, using the fabulous digi+ shield, so that I have a Toslink-Toslink connection to my DSP! The SW is the latest volumio version!
My problem:

The songs are played too fast, and too high, when I change the sample rate in volumio from 44.1 kHz to 48 kHz it is getting better, yet it plays them too fast (original: 3:18 is played in like 2:30). What could be the problem? Daniel from Hifiberry said, the probem could lie in the Raspberry or in the volumio software!

I would appreciate any help from you!

Yours Kai

Dear forum,

In an older version of volumio it works correctly when I select the DIGI options for the DIGI+ shield by hifiberry!
I tried an older version of volumio, the 2.185 from 2017-06-03. In there, I activated in playback options

Output Device: Hifiberry DIGI
DAC-Model: Hifiberry DIGI (DIGI+ is not available under this version)
DSP Over PCM: off
Audio Buffe 8 MB
Audio Resampling: off

This did the trick, it works and plays wonderful with my Audiotech Fischer Match 82 pp! However, I will test the latest version of volumio again and try to get the same DAC-Model as Hifiberry DIGI (which, I hope I remember correctly, did not work, but I will try again)
However, with settings not on the DIGI+, do I give away performance due to a lower sample rate (the DSP cn handle up to 192 kHz with 24 Bits, which I want to feed over the Toslink (I read in the blogs, that the DIGI+ shield can do this easily)?

Best regards
Kai