I used a new 2L flask for a starter 2 batches ago where I boiled in a pot and transferred the wort into the flask. The stirbar worked great at full power. My next batch I boiled in the flask and then cooled. When I started the stirplate I could barely get the whirlpool going because it kept throwing the bar off at maybe 50% power. I noticed the flask bottom doesn't seem flat. Could the direct heat have warped the bottom of the flask preventing the stir bar from staying in the center at higher speeds?