This is a daily issue for me as well on my HTC Desire 816 with Android 4.4.2 and app version 1.0.58. Most posts render normally, but approximately one out of fifteen are blank.
The only commonality I have been able to identify is that the unrendered posts tend to be long--I have not yet seen a short post that exhibits the issue.
I can click "edit" to view the markdown of the affected questions and answers; so far, the problem only seems to appear on the rendered version.
The issue manifests on multiple sites: StackOverflow, Programmers, English and others. It affects both questions and answers, but not necessarily at the same time. I see blank questions with normal answers, and vice-versa.
Closing and reloading the application does not change the situation. I have installed the latest updates.
FWIW, this question renders as expected for me, but the one linked by Shadow Wizard in the comments above does not.
Examples of questions that exhibit this behavior on my device: