IOS 8 Table View Controller performance issues?

After updating to iOS 8, my app has severe performance issues when scrolling in a UITableView - it didn't at all on iOS 7. It seems to lag or constantly jump a little.

It affects both older (2nd gen.) and newer (4th gen. Retina) iPads, but not iPhones, as my iPhone 5 scrolls fine through TableViews constructed in the exact same manner.

Important: It seems to only affect UITableViewControllers presented modally in a form sheet - not table views created manually somewhere else in a default UIViewController. Not even a modally presented form sheet of UIViewController with a custom Table View (as a property, for instance) is affected.

Instruments says around 3% of CPU time goes to cellForRowAtIndex method, with that one being the most consuming method. Of that 3%, 75% goes to the line.

Okay. After hours and hours of picking apart my app, I found the cause.

It turns out the problem was caused by the presenting View Controller, not the Table View Controller itself.

Here's how I found out, and how the symptoms connect:

It only affected native Table View Controllers because these were all presented by the same problematic VC. All other table views were presented elsewhere OR IN the problematic VC, which for some reason is okay.

It had nothing to do with the cellForRow-method or the class used to present each cell.

The presenting view controller is a full-screen iPad view controller with a lot of buttons. These buttons each represent an object in a room that one can tap for properties. This has been working fine up until iOS 8, where this thread started. For reasons I don't know, the buttons' alpha value of 0.7 made any presented Table View controller behave incorrectly. I found out by picking out elements one by one for the presenting view controller.

I disabled the line that set alpha for my buttons, and everything worked as expected and as it did on iOS 7.

I tried Google alpha-related issues with iOS 8 but got nothing.

Anyway - problem solved, albeit with the restriction that my buttons can no longer be transparent.