I did not know where the antenna was until you posted this.
It's actually a good place to locate it.. but proximity to the dash speaker.... yeah.. probably something with the install of speakers and amp messed something up.
I did not know where the antenna was until you posted this.The GPS antenna/receiver is located below what looks like a speaker grill on the top center dash and plugs into the back of the audio unit.
https://www.hondapartsnow.com/parts...e-lib-ka-cvt/gps-antenna-rearview-camera.html