I have similar problems on a mac running 363 in any browser connected to a 500 on a LAN, as I have to endure frequent disconnects that require closing the browser tab to restart the connection. It is not like the connection is degraded, as the stream can be over 7000kbps before dropping very suddenly.
There is no such disconnect problem when connecting via an iPad.
So it is interesting to see that testing on Windows revealed no issues. So it does seem like a Mac plug-in problem.
Also, the error code description for W202 is deceiving, as streaming on a LAN does not require the Internet, except when initiating the connection to the slingbox, so it is really not an "Internet" problem. I hope that support will acknowledge this is a known problem under investigation.
But I also hope they will introduce a way to avoid the need for an Internet connection at all when viewing on a LAN, by giving an option to specify an IP address or some other clever way to connect, as we had with the desktop client. Or let us use the desktop client with a 500. I would never use the browser for viewing if I could avoid it.
After wasting an hour with a chat support session with two support staff, trying to get someone interested in a debug log, here is a log excerpt showing what happens when the browser dies with a W202 error on a LAN to LAN session. Unfortunately, the support staff do not remotely have a level of technical sophistication to know that streams are not sent round trip to the Internet and back when viewing on the same network. I was finally told that an engineer would review this if posted online. Let's hope so, since he would not accept the log file directly like I would expect most tech support would do to escalate a case. Of course, the problem with this suggestion is that a log file contains personal information that should not be revealed, like, for instance, the finder ID, so I had to carefully examine this before posting. Hence, I have little good to say about that support channel, except that they handled themselves professionally.
Notwithstanding the error every 10 seconds about low memory, my own available RAM was over 3GB (out of 16GB). I don't see evidence of a memory leak in the Activity Monitor, but it seems that something is amiss here. Also, this steam of invalid argument and low memory messages occur all the time, not just right before a disconnect. FWIW, I have a dual monitor setup:
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