Was it working properly in the dual band setup and then didn't in the new 5.0 only or it never worked properly in either? Does a single TV have issues when others are off or only when multiple TVs are on?Based on info you provided it's not range so shouldn't be a band range issue. Probably not inference unless you're in a condo or apartment complex with the 5.0's shorter effective range and dampening through exterior walls. I have video optimizing enabled on some systems with AP22's, my own has 5 APs and 6 or 7 rokus and no issues but on systems with AP15s I never enabled it and those we just smart tv built in apps so on Sammy's and Sony's not roku.
Does your phone, tablet or laptop also lose connectivity? If so does it lose it if no TVs are streaming or does it just drop when video streams? Is it just losing WAN connection and LAN devices can still ping each other or do you lose both. If you have wired devices do they still work and see the internet or just local net or both?
There was an issue posted with video dropping that I think they believe was 1930-8G related so maybe try a different POE switch, try turning off video optimization as suggested previously, Personally I've never had any issues with AIO devices that I've notice or been made aware of and think they're pretty solid, don't recall what was the outcome of that post I mentioned but it to was about streaming video, might look for it, think they're were AP22s with a 1930-8G.