Out of virtual memory

We have a robot cell with 9 robots of various types in it. All have IRC5 controllers. Once every month or so, one of them will get an error that will pop up saying that the controller has run out of virtual memory then does an automatic warmstart. The mass storage only uses 1/3 of its space, RAPID memory is 90% free, and the system memory is mostly free. I am checking after the robot did its warmstart, so it may have cleared up something. I have seen this happen on 4 of the robots in the cell. Each time I cannot find any memory that is full. Does anybody know where to see the virtual memory? Is there a way automate the memory clearing itself without affecting production?