Create Vendor Admin Account - Config Issue?

I have a problem when creating vendors (Multi-Vendor v4.3). If I check "Create administrator account" it creates the vendor OK, but I get an error telling me "Password must be 12 characters long" (which is the password length set by default), and I have to create the vendor admin account manually.

I'm guessing it should auto generate a password in the background as there's no password field on the create vendor form, and this is less than 12 chars.

Is this a config issue? Can't find anything about this in the documentation.

Anyone else come across this?