In fact, I noticed the same problem during a recent demo for some partners. Using the trackpad, they were not used to increase the depth of zoom.
However, I'm sure it worked before. Therefore, it seems that updating Mac OS (or Safari) has violated this feature. This is good: support for mouse and trackpad in MacOs is in the list of Silverlight functions, MS usually fixes the problem, possibly for the next release (I suggest you cross your fingers)
Eilistraee
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