This is quite an interesting issue! For this problem, I would recommend checking to see if you get this issue on your TV using the same outputs to your TV. I would also recommend swapping out your video cables for another set just to check to see if they are working properly. Since you are experiencing this on several viewing devices, this could be a security setting on the router blocking the signal of your Slingbox from being sent properly.
If you have any other questions, feel free to respond or give us a call at 1-877-467-5464. We are open to seven days a week, from 10:00am to 10:00pm EST.
Hope this helps!
The Sling Media Moderation Team
I see Sling not only still doesn't know what's going on with this, but they're insulting our intelligence as well. "Cables"? Really? "Router Settings"? Seriously?! A useless answer is just as bad as a non-answer, Sling.
Anyway, I didn't want to say anything 'till I had a few days to play with it to make sure, but I'm pretty sure that this weekend I've come up with a solution for this problem. I'd gotten an inspiration by poster "rudnikda" that said the problem only seems to manifest itself when the TV (which is connected to the cable box via HDMI) was turned off. I discovered this to be true for my setup as well, which got me to thinking that it could possibly be related to HDCP checking(?) or HDMI port synchronization. I know that many of the HDMI splitter (not switch) boxes have to be HDCP compliant on their input sides so I inserted a 1-in-to-2-out HDMI splitter between my Cable box and my TV set and haven't seen the issue come back over several hours of Slingbox use. Since the HDMI splitter is always powered up whatever the anomaly is with the cable box component outputs doesn't occur and the PRO-HD doesn't lose sync.
The reason I didn't want to report back yet was the HDMI spliitter I'm using is a relatively expensive box that I'd only chosen 'cause it was the only one available at the retailer I'd gone to, but I have a cheap (~$14) unit from Amazon on the way and if that works then I'll certainly report back here so that other users will have a REAL solution for a problem that's over TWO years old that Sling has chosen to ignore.
My workaround of inserting an HDMI 1-to-2 splitter between my cable box and my TV does fix this. I found a cheap, self-powered $15 box on Amazon that I'm currently using now: http://www.amazon.com/gp/product/B00DTWX2NI/ref=ox_ya_os_product and it works.
It's a shame we have to buy something to fix this issue, but as Sling has been useless troubleshooting this at least it's a cheap fix.