Proxy Users disappear (8 out of 10) in one Mailbox

Strange issue here:

One user has 10 Proxy entries in his mailbox. Since last week, 8 of them disappeared. 2 are still there.

User again created all proxies without problems. Today the 8 proxies again disapeared (happened twice). The 2 left proxies are the same as last week.

Hint: Last week we deleted one account (user left the company), this account was proxied before by this user, but the deleted user was automatically deleted in Proxy list. (see

GWCHECK says everything is ok with this mailbox. Is there a hidden (misc) option we can run?

Client 14.2.3 btw...