I read much about the issues with the DS380 after I encountered power-on issues under certain conditions depending on the number of connected HDDs.
It turned out to be an issue with the DS380 backplane (the board in the rear of the HDD cage) and after contacting SilverstoneTek I got it replaced one week ago, everything working fine now.
Sadly I realized that besides setting some BIOS settings there is no possiblity to control the fans from XPEnology,
even with ipkg installed sensors etc packages (those show only the CPU cores, nothing else!)
Some guy from another project pointed out, that they are observed and controlled by the BMC, and can only be influenced using IPMI commands.
(https://lime-technology.com/forum/index ... ic=39238.0)