UE5.1.1 this still works. I haven’t got a project currently in 5.2 but I see massive changes to the SpinBox.cpp file. There is a lot of b*llshit going on between the UMG and Slate widgets in how values are set and retrieved, often resulting in loss of data, incorrect values or values being stored in multiple variables.
I’ll add this to my list of largely ignored Slate synchronisation issues so we can perhaps motivate EPIC to get a new department for UI development 
. They can’t stop breaking things it is ridiculous and must be said. They simply don’t test their changes it’s the only explanation.
[Bugs bugs bugs] Slate widget synchronization
EPIC, please stop breaking Slate and UMG in new releases.