Bug? Blueprints "Compile" have "Endless loop" -> Widget Component Class doesn't save

I have two blueprints, and when I compile the first one, the second is marked dirty. If I compile that one, the first one again is marked dirty… And so on.I think this is the reason why under “Add Widget Component” the setting “Widget Class” doesn’t gets saved. Everything works ingame, but as soon as the engine restarts, the property is reset to “None”, so I have to open EVERY BLUEPRINT that uses this node an re-select the Widget Class. Reaaalyy annoying. What could cause this problem? Is this a bug? Both Blueprints have no Construction Script…

Blueprint A is a Card-Representation (like in a TCG).
Blueprint B is a Deck, eg multiple cards that are ordered in a specific way.

Each card has a parent Deck, and each Deck has multiple cards. This is the only thing “special” about this both blueprints, but this can’t be the problem, no? I mean, why should it…

Please help me, it is impossible to continue the work on my project without resolving this bug.

Unreal Version: 4.7.6