Some systems of logical equations contain identical equation variables that cannot be linked with arrows and recombined. In this case, you cannot ignore their repetitions and use the usual display, because contradictions will appear in the process, and it does not matter whether these variables were previously taken into account explicitly or by duplicating arrows.
To avoid inconsistencies, you can save such variables by substituting in the table next to others, and display until they are no longer needed. Now, if contradictions arise, they can be immediately eliminated.