Can anyone explain this electrical anomaly?

We are having issues with our home electrical. We occasoinally see a "brown out" which until recently was easily resolved by flipping the main. However, over Christmas this stopped working, and we ended up having our conduit replaced. Yesterday, we experienced another dip, except this time the power would come back up when we ran the dryer then fluctuate as the thermostat in the dryer cycled. We then unplugged the fridge to put it on an extension from the neighbor's, and the power came back full, with some occasional flickers throughout the night. So, in essence, when the fridge was plugged in we only had full power while the dryer was on and heating. This morning the electrician found one leg of the main breaker tripped, even though we had checked it last night. Now, before the electrician sorted that, I showed him the phenomenom of the dryer situation and he initially was concerned that something had become "neutral" and was somehow feeding electricity back into the house. What? Can anyone weigh in on this and help me understand? Thank you!