Audio trouble (looking for advice)

[HTKY!]

Gonna get right to the issue here.. Was using a smsl q5(0)? pro to power my Klipsch r15m stereo bookshelf speakers and a Klipsch sw120.. Everything was fine but I wanted a headphone out and Bluetooth so I upgraded to the computer topping mx3.. I also changed my speaker cables from some self made ones to proper micca 14 gauge wires and a longer sub cable to position the sub further away.. Everything works the same except for two issues.. First issue is that when I turn my amplifier off my sub bumps twice pretty hard, enough that it actually startled me the first time.. The only change to my sub is the new cable that is single ended instead of Y split.. The other is whenever I try using foot bar to play music it gives a pop up saying the device isn’t detected (was working perfectly fine up until I switched devices). I can give some more specific details like the specific cable for the sub I had before and after and the exact message I get on foot bar after I get back home.. Just hopping to get some suggestions as it’s inconvenient to have my sub bump so loud whenever I turn it off (I live in an apartment lol)