Commie groups and individuals fight and argue with each other all the time.
...most often behind the scenes.
Once the left takes power, then they fight over who controls the power. Eventually, in most cases, it comes down to the control of one strong man, such as Lenin, Stalin, Pol Pot, Mao, Castro, Maduro, Tito, etc.
It is pretty much built into the system. If the party needs to rule the people, somebody needs to rule the party.