Attributes "disappearing" in Act 4

When entering maps in Act 4, character attributes are being reduced unexpectedly, causing skills to stop working due to unmet requirements.

For example, my character has 54 Intelligence while in town or outside the map, but as soon as I enter an Act 4 map, my Intelligence drops to 46. Because of this, some skills that require higher Intelligence become disabled.

This issue seems to happen consistently when loading into Act 4 maps and significantly impacts gameplay.