In single player.
After placing a sign, sometimes the text you write on it disappears after closing the sign editor. Additionally, the text sometimes flickers visibly once after closing the editor. Often the problem only happens in some blocks: you can try editing a sign in one spot ten times, and get nothing, while a sign in the next block over edits just fine.
After writing something on a sign, the sign does not flicker or become blank.
After writing something on a sign, the text on the sign sometimes appears to flicker, and sometimes it does not reappear, leaving the sign blank.
1. Place a sign
2. Write something
3. Close editor
There is a chance that the text on the sign will appear to flicker and/or blank out. Happens unpredictably, but rather often for me, and in some arbitrary block locations more often than others.