Follow Feature (Sometimes) Does Not Work - Bug?

There are some steem accounts, which I want to follow but something seems to be wrong with the execution of follow commands or follow/unfollow button displaying.

Example:

I want to follow steem accounts @zipporah and @zyx066.

---

I click Follow button on @zipporah profile and Follow button of @zyx066, which is one of her Top Reblogged Users (shown in the column on the right side).

The command executes as I get following screen. Both accounts seemed to be followed by me now.

SteemWorld: ok

Steemd: ok

Everything seems to be working fine, but when I refresh the page in browser or revisit same accounts later on, it looks again like I'm not following the two featured users from this post.

Is there any particular reason for this or is it just some bug in the blockchain?

I don't know how the 2 users see this, but they probably get the message I started following them all over again (at least in Notifications section in Busy.org). And this must be pretty anoying to see, and I appologize to any such user for just wanting to follow them.

UPDATE 1

Github Issue: https://github.com/steemit/steem/issues/2846

UPDATE 2

I just realized one thing, which might help @timcliff, solving this problem. All the "problematic" accounts for me start with letter Z, meaning they are all at the end of the alphabet. I know some people who have trouble following me and I also start with letter Z.

It seems that if I follow many persons and try to follow newly somebody from the end of the alphabet, this doesn't properly show in follow/unfollow buttons. It looks like a time related issue in combination with number of people followed. Try to think in this direction, maybe there is something to it.

Example: I just started following @zainal.bacee for first time ever just for test. I see myself in his list of followers, but the follow/unfollow button says I'm not following this user.

UPDATE 3

Github Issue: https://github.com/steemit/condenser/issues/2996