It is possible to have insufficient adhesive and the solder tension from
the wave washed the parts away. Do the glue dots have a mounded or flat
appearance? How are you dispensing the adhesive? What component
packages are you seeing this with (1 type, various types, etc). What type
of wave machine do you use? Is it a flat wave or angled? Do you have
a chip wave also operating at this time? What is the speed of the
conveyor? What is the wave depth?
Kathy