Category isn’t shown for email in Sent Items.

Hi,

I have account in Office365 and use MS Outlook and sometimes OWA.
I use Category to mark my emails in Sent Items folder.

So scenario 1 (work properly):
1. Open OWA, run Outlook
2. Create and send new email by OWA
This email appears in Sent Items folder in Outlook and OWA.
3. Find the email in Sent Items and set a category for this email by OWA.
This category appears in Outlook too.

That’s right.

Sscenario 2 (doesn’t work properly):
1. Open OWA, run Outlook
2. Create and send new email by Outlook
This email appears in Sent Items folder in Outlook and OWA.
3. Find the email in Sent Items and set a category for this email by OWA.
This category doesn’t appear in Outlook at all!

That’s incorrect.
It doesn’t work if Outlook is connected in cached mode.

Why is it happened?
How can I fix it?

Thanks.