That doesn't sound good at all!!!
There are basically two possibilities as to what causes scale loss. Water quality, and external factors ie tankmates or decorations.
Please answer these questions, we can't give you any sort of an accurate answer without knowing this info:
Tank size:
Make and model of filter(s):
How often do you change the water:
How much water do you change:
What's the ammonia:
What's the nitrite:
What's the nitrate:
What's the pH:
What's the KH:
What's the GH:
Name all the tankmates (species, type (ie oranda, comet, pearlscale, apple snail):
Are there any ornaments he could have gotten stuck in?