4000 isn't the limit. 30000 is the limit
What model Comand do you have?
I have yesterday had the firmware on my NTG2.5 updated to what the dealer tells me is the latest firmware (version 07/51/09/29/00).
Whilst it now recognises my 32gb card (previously it would not recognise more than 2gb), it does not read all the folders and files - it stops at the 256th folder. So, I am stuck with a 256 albums limit.