I'm on a realm world with seed -912478101.   I create an Observer clock, at 258, 62, 259 and 259, 62, 259.  The observer clock ticks about 5 to 10 times per second, inconsistently but like you'd expect.

If I then move to 251 62 260, I place another observer down on X=253, I can see the redstone light on for a long time – for about 20 seconds.  If I put an observer in front of it (for the purposes of creating another clock), I'll continue seeing nothing for a while until the signal turns off on the new observer.  Once the signal turns on on the new observer, it continues taking about 20 seconds to pulse, but that ALSO makes the other observer clock go slow.  (Deleting those observers and replacing the first set allows them to pulse regularly again).

I don't have a lot in this chunk – maybe a dozen hoppers and a 40-or-so-high bubble column feeding into them.  It's for a mob farm.  

I took a video of it that I can make available, but it's 250mb and I can't upload it here.