Thank you , I will contact customer support .
It is easy to reporduce thecase.
Step1: Create a new cell & draw a rectangle shape & stream Out (Stream Out From Virtual Memoey is "off" & No flatten pcells)
just use the default set.
Step2:Instance a cell (library/cell which is read-only) , Edit- in-place,use the Rulee to measure some shape
Return to top (no save)
Step3: Stream out again , you will see the message (Save the following data befor closing ? ...)