Here's another gotcha I have found in a project I moved from 3.0 to 5.0.

In one of my form, I had a grid having a relation on a combined key.

In 3.0, I was having STR(DEP.DEP_ID)+STR(TEMP.CAT_ID) but this is not working in 5.0 as it seems that multiple aliases in a relation is not supported anymore. No bug appeared but the full table appeared on the grid without any relationship.

To make it work, I change the key to STR(DEP_ID)+STR(CAT_ID).

I guess I should start Universal Thread Gotcha forum.