This is a really interesting post! Because I (also) have Cubase 10 Pro and the same issue only occurs on Win10 Pro (Lenovo T480s). Everything works completely fine on two other computers (2x Lenovo T440s with Win8.1). So this is maybe a problem with MIDI on Win 10?
(Just for the record, I also had this issue on Cubase 4 on WinXP and the “Use System Timestamp” option solved it.)