We encounter a problem (error) for quite a simple Process Builder.
Let me explain the situation:

We have a Managed Package which we have deployed in a new Org. In the Dev org we would like to change a Process Builder. Therefore we created a custom field, named "Date of Prenotification". We also created a new Process Builder which should send the Prenotification, add a completed Task and update the "Date of Prenotification" field. Updating the field gives an error. Part of the criteria is that the "Date of Prenotification should be empty. No problem. Selecting the field in setting up new value (in the Action) is also no problem but when we want to save the Action an error occurs:
The field named Opportunity.frnpc03__Date_of_Prenotification__c can't be found.

I hope someone knows this issue and can help to solve this!

frnpc-03 is the Prefix of the managed Package.

We have created a Package in a Developer Org which we used to deploy with our customers. Suddenly we receive a notification and error when we want to add items into the Package or deploy the package. The notification is: Bad Reference found.  See belowPlease press Recompile All or edit and resave the following items. When trying to recompile All we receive an error: An internal server error has occured.  See below


We have several developer Orgs and this issue appears in all Orgs.

Does someone know what we can do so we can create/edit and deploy packages again?

We have created a Package in a Developer Org which we used to deploy with our customers. Suddenly we receive a notification and error when we want to add items into the Package or deploy the package. The notification is: Bad Reference found.  See belowPlease press Recompile All or edit and resave the following items. When trying to recompile All we receive an error: An internal server error has occured.  See below


We have several developer Orgs and this issue appears in all Orgs.

Does someone know what we can do so we can create/edit and deploy packages again?