So, I have some new information, well kind of new. One thing I neglected to mention is that with my old setup I was using a PoE splitter to power the Pi and provide ethernet. The particular adapter I was using was a 10/100. I decided to take it out of the equation with the 3b+ by pulling out my old power adapter and plugging the ethernet cable directly into the switch. With that, the problem went away without any software update.
So I’m wondering if my issue is that the ethernet adapter was struggling to negotiate with the switch about speed with the 10/100 limiter between them. I suppose it could be power related, but I haven’t gotten a single lightning bolt with either the 3b or 3b+ with this config.
Anyway, I’m going to leave this as is and call it solved. I’m planning on getting the PoE HAT when it comes out, so I can run this way until then.