Issues related to improper nozzle/feeder maintenance or use of poor quality nozzles are often the same. Here are some of the most common problems:
1. Poor pickup location on part. It will cause a loss of vacuum and result in parts shifting on the nozzle during transport.
2. Short/worn nozzles result in poor pickup and can cause the part not to be imbedded into the paste. When the part is not placed into the paste correctly there is not enough surface tension to hold the part while the PCB is moving. Parts will shift.