Those connections are my understand as well. I use Apple Car Play so always have my phone hardwired to the bike and bluetooth between the phone and bike turned off. That is one factor.
Wonder if you are seeing a problem similar to the CB interrupting the rider passenger non-mesh intercom issue. I use the +Mesh paired with the SRL2s to work around that issue.
Look forward to hearing what you discover and about the jell ear plugs.
The Shoei Neotech II and J Cruise II helmets that I have both have dedicated speaker holes. I placed the the speakers in the holes, no pads cover the speakers and they are flush and level with the helmet interior, not slanted.
With the 50s, had to max out both the Honda and the headset volume and still couldnt hear at highway speed. Sena thinks it might be a bad headset.
With the SRL2, had hedset volume set at about 75% and Honda set at about 75% for each of the volume controls (audio, CB, Nav, ACP, ect). I did notice that the CB can cause the volume level on other "channels" (Nav, audio, ect) to go lower occasionally. Just have to cycle the CB off and on to get it all to reset back to "normal".