Anytime your grill shuts off with an error or loses power and is not able to shut down properly check the burn pot before restarting. The errors are there for a reason.

When you try to restart your grill with a pot that has residual fuel the air flow is restricted therefore it can’t breathe properly, it's like throwing a huge pile of leaves on fire. It will smoke like crazy. Smoke has gases in it. Once the pellets do ignite all these gas will ignite. Just like leaving the gas on your grill too long with the lid shut as your trying to get the igniter to ignite. As the gas builds when the electronic igniter does ignite you can get a small explosion. Opening a lid on any grill propane, pellet or otherwise during startup is a good and safe practice.