I believe I experienced this same bug today. I was able to plan a route no problem before linking my live car data in (I have a 2020 Bolt and I'm sending data via webserver upload in Torque Pro) but trying to revise the plan later in the car partway through the trip while waiting for a charge resulted in the "planner server error" message via the app or web interface. Force logging out the website and refreshing did allow me to plan routes again, but only with manually entered car info instead of live data. I submitted a bug report via both interfaces when prompted, but didn't know what other information might be helpful at the time so the reports are default. After reading this thread, the described problem definitely matches my experience.