Using a multitester, the Vdc output voltage of the PSU, ref. 9386, seems to be 24V instead of 18V. Can this voltage harm the LNB?
The power supply unit, ref. 9386 does indeed generate 24V, but when it has been loaded, it generates 18V.
To verify this, you can insert a splitter with a DC bypass in its outputs between the PSU and the LNB (such as ref. 7304).
Now measure the voltage in its free output with a tester.