Too many negative connections on battery?

[Rounded_nut]

So here's a quick question, between an apu, inverter, trailer aux power and then engine needs, my 3rd battery negative terminal is a busy place, the nut can still get on alright but lots of connections. I've been having some issues with fluctuations on apu alternator voltage and I'm wondering if that can be a source of issues? I'm thinking I might need a small bus bar to do the connection to the negative, and from my understanding to get the max power you need to connect the 1st and 3rd pos and negative. The trailer aux power has a huge draw for a hydraulic pump, inverter, well that's thirsty too, and for proper charging the installation manual says first and last. All ground connections check out and are clean, same voltage at battery and apu.

Thanks for any assistance!