Acrobat reader trusted root issue

While working with Acrobat Reader DC Version 2018.011.20040 below Win 10 the Application hangs if I try to sign a document with the readers internal digitally signing tool. It has the same effect if I open an existing but signed one. Or if I try try to view the certificate while signing the document.

Until January 2018 it worked well.

For signing I use the user code signing certificate issued by our own Windows CA. It's a V3.0 CA version.

Then as trusted certificate I use the root certificate of our CA.

Acrobat reader hangs as soon the certificate is checked our "touched" but only if the root certificate has been marked to be used as trusted root. If not I can open or sign a document.

If I use a user certificate as activated trusted root the effect doesn't occur.

Is there anybody who has an idea what the cause may be?

Would be great.