I had completed a series of sequence diagrams with many arrows, each had a description consisting of several space separated words. To unify the messages I added a class to a lifeline then for appropriate items most wer unspecified or self message I created a method call with the same name as the message text.:
Originally looked like: “20. send message body” then became “20. send message body()” as expected after creating classes and method throughout all the diagrams.
However after closing the VP program and reopening it the next day I found many of the arrow descriptions items blank i.e., just “20.”. I had to double click each number and select the method from the drop-down.
I think the drop-down cointained most the methods I had created (a couple might have been lost - not sure, as a lot of them became blank). All the affected arrows were properly set to “call”, just the method lost.