Multiple scattering can lead to artifacts in dynamic light scattering data and is caused by high sample concentration: With increasing particle concentration, the probability increases that scattered photons will get re-scattered by other particles before reaching the detector (see image below). The result will be faster intensity fluctuations and smaller apparent particle sizes. To investigate if multiple scattering influences the results, record DLS data from a dilution series of your particles. Deviation from a linear concentration dependence towards smaller particle sizes may indicate multiple scattering:

Since DLS measurements on Prometheus Panta are carried out in thin glass capillaries, the scattering volume is close to the capillary wall. This has the advantage that the light does not need to travel a long distance before reaching the scattering volume which in turn reduces the risk that multiple scattering occurs.