Hi Mista Nige,
Sorry you found other posts without an answer - they weren't intentionally ignored!
With the firmware version 1.05 there is a notice:
After updating the DDJ-1000SRT firmware to ver.1.05, Sampler Master Volume level of Serato DJ Pro does not sync with the SAMPLER VOL knob on the DDJ-1000SRT. If you find that the DDJ-1000SRT Sampler volume level is not appropriate, even when turning the SAMPLER VOL knob, please adjust the Sampler Master Volume level in Serato DJ Pro on your PC/Mac. For details, click here.
Unfortunately this is a change that we cannot control as it has to do with the software output.
Make sure your sampler output is selected for the appropriate destination within Serato and it should work when adjusting the levels in software.
Thanks for your understanding.