I start a combat in the Shattered Ruins with the goblins on the first room where Priestess Gut is located, then I use the flute to call Lump and his friends to join in the fight... So I now have 3 beefy ogre allies to help me during the fight so I don't want to "waste" the help I got, I make my way to the room where Mithara is located to get them in combat, but as soon as I get too far away from the "main fight", the game gets really laggy as in I can make nearly infinite movement with the character that is far away and the combat commands won't compute, not only that when I press end turn it takes around 1 to 3 minutes to end that characters turn, and everytime it is that characters turn or I get too far with another the same thing happens.
And all that happening and the game is not even using 30% of my ram nor 40% of my CPU, so I don't think is my PC not handling so much "processing" of the game.