Here is the origin node, in some situation we set the value to 1.0
When we compile and save the blueprint, there is no any error occur.
However, if we close the Unreal and reopen the blueprint file, it gets compile error. The message is shown below:
We also find the false node have been changed, and we can not type constant value as previous version.
Regenerate a new select node and re connect , we found that the node type is float.
The select node with compiled error has ref float type seems due to the return value connects to a ref integer type.
Our suggestion is, if the reference type will not match after reopen Unreal 4, Unreal should trigger compile error at the first time. The error is usually detected until the blueprint has been submit.