I am using ubO too, I just purged the cache and updated the filters, still experiencing the same issue. Maybe YT is still testing this and haven't rolled out the blocking on everyone just yet?
Go on the unlock origin reddit, they have clear instructions for getting it working.
Basically disable all current ad blockers, including YouTube enhancer ad blocker, reset filters to default, make sure there's no cosmetic filters either. And it should work L.
I've yet to encounter these also. I've assumed it's just been luck with the A/B testing.. But perhaps it could also be that I've never allowed doubleclick.net scripts to run in NoScript, or that my ublock-origin setup has taken care of itself, or that because I've actually participated in youtube's other non-premium monetization schemes (channel memberships) from which they take a 30% cut and they want to upset somewhat paying users last.