To reproduce:

• Open wb
• Create an new object, call it Schedule, give no fields, open the optaplanner dock and annotate it as a Planning Solution.
• Close and reopen wb
• Open the object Schedule, create 2 fields that are both lists, click on the last field and then open the optaplanner dock.
• It says that this object isn't an entity or a solution, so no options are available. => WRONG
• click on Schedule, see that it is
• Click back on that last field, and now that message is wrong and you can change it.