Yea we did a polarity test, everything came out normal. This is where the problems start though, everything is set properly including the processor but nothing is working well. Both of us think it's that PAC adapter. But we don't know, from what my installer told me, is that the adapter is only used for the controls, it could lose some audio signals on it (-2 to -4 dB), but it shouldn't do that. We are thinking that replacing the Audiocontrol DSP with a Helix to see if that fixes the issue but we don't know. I've been in audio engineering for 15+ years, and I haven't seen this issue before.
The other question is to get a better audio sound, is it worth replacing the built-in head unit?
Golvery Bluetooth 5.0 Receiver for Speaker, Wireless Audio Adapter for Home Audio Car Stereo with 3.5mm RCA Jack, 16 Hours Playtime, Dual Connection to 2 Cell Phones, Easy Control On/Off Slider
You may want to test something like the above plugged in as the audio source into your DSP thereby eliminating the HU & PAC adapter prior to DSP then play the same source material thru bluetooth to see if this corrects issue. I know the non-JBL pioneer HU on my RAV4 requires no PAC adapter since it outputs analog audio. I take it your RAV4 has the OEM JBL system with HU that only outputs digital which is why the PAC adapter is needed for the D/A conversion?