Generally, maintenance is what you do to prevent a breakdown and repair is what you do to fix a breakdown. So the more effective your maintenance is, the fewer resources you must allocate to performing repairs.
Typically, the maintenance department handles both functions. It follows from this that if maintenance gets too busy doing repairs, it will lack the resources to perform adequate maintenance and a vicious cycle ensues.
One way to prevent this cycle is to determine what training is needed to develop repair specialists for critical equipment, and then get them trained. It isn’t necessary to train everyone in everything, nor do you want the same few people to get all of the training. Let different people own different areas of expertise.