Signing with Certificate Save Dialog not opening

Hi.

We are using latest Acrobat Reader DC 20.x on Windows 7 and 10 all x64.

We use Gemalto G30 Gen2 Certificates on USB Dongles to sign pdf documents.

In most cases, it works perfectly, but there are few instances where it simply doesn’t work.

It stops after selecting correct Certificate and ‘Sign as "XXXXXXX"’ form opens (image attached).

When you try to click "Sign" button, nothing happens. Sometimes it seems that mouse pointer shortly disappearing and appearing again. Normally, Save dialog is opened.

We updated Smart Card Reader driver, reinstalled Acrobat Reader DC, tested Certificate with SafeNetAuthenticationClient and it works normally, Windows OS normally recognises Certificate and it seems that Acrobat Reader also, as you can see all Certificate meta data.

Windows OS on all these computers is being updated regularly as part of domain group policy.

Any suggestions?