1. Friar Laurence's Late Message: Friar Laurence sends a message to Romeo in Mantua, informing him about Juliet's false death and the plan for their reunion. However, this message is delayed by the plague and doesn't reach Romeo in time.
2. Capulet's Change of Plans: Capulet initially plans to marry Juliet to Paris on Thursday. However, without informing Romeo and Juliet, he moves up the wedding to Wednesday. This sudden change leads to confusion and complications.
3. Juliet's Fake Death Message: Friar Laurence gives Juliet a potion to make her appear dead, so that she can be transported to Mantua and reunite with Romeo. Unfortunately, Romeo doesn't receive the message explaining the plan and assumes that Juliet is actually dead.
4. Failure to Deliver Friar's Letter: Friar John fails to deliver Friar Laurence's second letter to Romeo in Mantua due to difficulties caused by the plague and is detained in Mantua. As a result, Romeo remains ignorant of the plan to fake Juliet's death.
5. Incorrect Assumption about Juliet's Suicide: Romeo discovers Juliet apparently lifeless in her tomb and, believing she has killed herself because she found him, takes his own life. However, Juliet was not dead but still under the potion's effect, and she awakens to see Romeo dead next to her.
These miscommunications play a crucial role in the tragedy of "Romeo and Juliet," as they prevent the characters from fully understanding their situations, leading to misunderstandings, rash decisions, and ultimately, their downfall.