Dependent Fields are not yet compatible with Lightning Experience when using Sales Path
|Knowledge Article Number||000230610|
|Description||If Lightning Experience is enabled in Salesforce, using Sales Path on Opportunities will mean that dependent fields on the Opportunities layout will not work.|
|Resolution||For example, if there is a dependent field based on Opportunity Stage, when changing the stage using the Sales Path, the dependent field will not automatically update.
Until this functionality is available, workarounds include: