Can't see content on reading pane or double click

[waseeyasn]

Last saturday we was upgrade zimbra to 8.8.15
Today, I search old mail, but some mail can't read content in reading pane or double click,it's blank (not all).

But I can see the content in mail subject(as the attachment).
Does anyone have the some question?

I try to change 「preference setting」→ 「mail 」 to text mode, it will normal.

IE version :11.345.17134.0
Zimbra version：8.8.15