You are probably just experiencing what is described below which is completely normal with the Arcana:
 

From the Arcana manual FAQ:

I notice a short black screen / resync when starting a content that i didn't have or noticed when connected direct to TV?
All that is normal, you will have the same if you insert any device in between, like an AVR, splitter, matrix, switcher, video processor, and the more device you have in the same chain, the longer this will take, the only way to have that nearly not noticeable is SOURCE > DISPLAY direct since signal goes straight to panel driver. If menu is 60Hz and content 24Hz then there will be a resync like for any video format change, if you have SOURCE > TV, then sure you never noticed it but insert any device in between and you will have the exact same, just normal, HDMI resync.

Thanks for finding that out for me….

It does seem to ease off after watching the channel for a few minutes, but every time I switch to the Sky Q main menu & back again, there is a slight delay….

Is there an actual audio delay or does the sound just cut out for a few seconds while the Arcana is resyncing?

It’s an audio cut off, which would make sense with the info you sent me….

Another strange thing I noticed is the Sonos S2 app is no longer showing my Arc/Sub/One SL rears on the app?

Ive reset the app, but still nothing showing up on the app?

Unplug the Arc for about a minute and reboot your router and phone.

Do you leave your switch on all the time or is it safer to put into standby?

Whichever you prefer, or whatever works best for your setup.

Ok.

As always, thanks for your help….

Hay all. I have the same problem, I have an LG C1 Oled with the Sonos arc and a UB9000 every time I play any DVD with DTS ITS IN Stereo PCM 2.0 only, it’s driving me crazy now

The TV is set to pass through as well. 

Check out this thread @SeafordMick . You might not find the greatest news, but it might help you try some things and/or understand the situation a bit better. I also have a UB9000, but a G1 instead of a C1. I believe the problems would be the same for you. In a nutshell if you don’t want to try the stuff mentioned, we can get DTS conversions to Multichannel PCM with some effort (and more gear), but it always comes through as 7.1 which leads to some missing sounds. Sonos has mentioned that they are working on downmixing to 5.1, but no timetable. I’m hoping soon.

Has sonos sorted this downmixing issue out yet, does anybody know? I know since they have released basic DTS support but wondered if this issue has been fixed and if I use a blu ray which has 7.1 what will that come through as? 

I noticed recently that the application correctly displays 5.1 at least sometimes. I haven’t updated the Sonos equipment or the app in awhile though. I have everything on 14.10, so I’m not sure about the latest software. It seems to be working for movies and on the Nintendo Switch. I haven’t done any deep testing on it, though. It has been claimed to have been working all along, so perhaps just a display error on the application side. I’m still using the Dr HDMI 4K to get it from the UB9000 through the LG G1 to the Sonos soundbar, though. I haven’t noticed any issues, just have to turn it up really loud for DTS audio surround movies in comparison to Dolby tracks.