Zimbra, error uploading file. why?

Question

Zimbra

on Monday morning on 3 mailers under the zimbra, the web muzzles first fell off. When entering in AJAX mode. Or rather, after entering the login password, nothing further happened to the users. But the admin web console worked. White screen as they say. It was possible to enter in HTML mode, but I noticed that there were no "pictures" of the names of menu items. I understand they are loaded from outside. After lunch, web muzzles started working. But when you try to attach at the moment ... writes "error uploading file". All worked on versions 8.6.0 und 8.7.0. open source. But at the same time, mail through mail clients like Thunderbird plowed and attachments normally stuck (and plows now).
The question is... in which Zimbra logs should I look? There are such a bunch of them. In "regular" (mail.log, error_mail, zimbra.log..etc.) does not write any alarms about AJAX.
On one, I had to stupidly rearrange Zimbra to a fresh one with the preservation of mail and password hashes (there are good scripts).