Having the same problem at several customers, they are all up to date at UTM 9.506-2.
One SW version is giving the problem, others on a SW version are without the problem.
One SG115 is giving the problem, others with an SG-115 are without the problem.
The problem only appears in Chrome. The problem also existed in previous versions of UTM (9.4, 9.3, etc.)
Is there any solution?