Why does iTunes hang when updating songs and videos?

[iMore Question]

iTunes hangs when updating songs and videos

Hi,

My iTunes (12.3.1.23) always hangs for 10 or 15mins every time I try to update song information e.g. adding album art. Does anyone know why this is the case. It's been happening for months
My system specs are
iMac - Retina 5K, 27-inch, Late 2014
Processor - 3.5 GHz Intel Core i5
Memory - 8 GB 1600 MHz

My library is stored on an external Drobo hard drive

Cheers