I'm faced with the same issue, but not sure how to add the char press delay described - any further direction?
I've got a similar setup: HP Spectre 360 running Win 10 with Veracrypt v1.23 and using YubiKey to enter the pre-boot password. My issue is that regardless of the password length (tried 64 and 32 char) I program into the key, VC only accepts the first 16-20 characters before moving on to the PIM (still not sure what that is) and the authorization fails. I can still enter the (very long, very complex) password manually for access. The Yubikey dumps the complete password into a text editor just fine,...