The phrase "goes haywire" refers to a situation when something unexpectedly stops working or goes out of control. Some synonyms for this phrase are "goes awry," "gets out of hand," "falls apart," "turns chaotic," "malfunctions," "breaks down," "loses control," "runs amok," "goes off the rails," and "slips up." These phrases can be used depending on the context and severity of the situation. For example, "goes awry" is a milder synonym compared to "runs amok," which suggests something has completely spiraled out of control. No matter which synonym you choose, the implication is that things are not going as planned.