Error reading file Yandex-disk. What is the problem?

Question

Yandex.Disk

Windows 7, the latest version of Yandex Disk. Through the web interface, everything works, I throw files there, everything is synchronized. I delete - they are deleted on my computer. But if I throw any file from the computer - a reading error. Moreover, if I throw a folder with subfolders - the whole structure appears on the web, but there are no files themselves, for the life of me. In the help (error reading files) they say either about access to the folder, or that the file may be occupied by another application. Well, firstly, I installed access, and secondly, it obviously exists - after all, after changes in the web files, they are synchronized normally. I can easily delete files and so on, just in case I checked Unlocker - everything is ok. Files, I repeat, any - a text document, a picture - it doesn't matter. Even the added screenshots are not synchronized by the Yandex disk itself - an error reading the file of such and such.
Who had what helped?
PS I also use Dropbox, I wanted to use Yandex exclusively for backups and materials like photos. I will gladly take advice about another free cloud service, you need a minimum: a windows application, synchronization between multiple computers, a web interface, stability. For everything else, I have a dropbox.

Answer 1

The answer was prompted by the support service, the problem with the Yandex.disk client is due to the version of the antivirus:
Kaspersky Endpoint Security 10 for Windows, I have one at work and at home.
They promised to fix it in a new edition.