Your main issue are the antennas, having them so close together is what reduced the performance.
Also the fan wouldn’t be an issue if it wasn’t directly next to the antenna.
Well could also be that it’s feeding back through the 5V rail because the SDRs aren’t great.
Build yourself some quarter wave antennas that can be place at least a foot apart and a foot above the pi.
QUICK SPIDER - No Soldering, No Connector
You can just make it a bit longer for 978 but it’s not that critical anyhow with this type of antenna.
Would improve your reception a lot.