The gr.a, iI.a, iL.a are obfuscated internal mendix java class and method names, so just skip them. Most information is in the error message. Stack is harder to read.
I should recommend adding and Error Handler microflow to the actions that retrieve the lookup object. This kind of error may happen when the object is in memory but not (yet) commited to disk or reverse. Read the documentation about the difference between retrieving in memory and from database and assocations. Other option is to check the security, but that will often lead to end-user security error messages.