Wrong validation in Calculated items for Aggregated/Math functions.
1. Create agent ITEM with value type Text.
2. Create calculated item:
jsonpath(avg(/HOST/ITEM,#1:now-5m),"$.[0].last_name","lastname")
3. Result: Item is successfully saved.
Expected:
Incorrect item value type "Text" provided for trigger function "avg".

This validation works fine in triggers.