Iron golems not dropping scrolls [4.40] [SMP]

[The great randomo]

On the server I play on, I've used the iron golem farm excessively. At first, it seemed to be working fine and knockback arcane scrolls would drop once for around every 15 stacks of iron.
However, ever since the 4.40 update, the scrolls do not seem to be dropping at all. It's not that enough haven't been killed - I've probably got another 25-30 stacks, but none are dropping.
What's causing this?

[Graphite]

Let's see whether I still remember the math for this:

One scroll in 15 stacks of iron is 1 scroll per 960 iron, so a chance to drop of 1/960. This translates to a 959/960 chance to not drop a scroll. The odds of a scroll not dropping after 30 stacks of iron is (959/960)^1920 = 0.135, i.e. 13.5%.

All in all it still seems reasonable that you're just having an unlucky streak.

[BlackCat]

Sorry for the late reply, I actually did some testing with a few iron golem farms set up, I believe graphite is correct. You're probably just getting unlucky.

Just thought it would be helpful to have some more reassurance, sorry about your knockback woes.