I recently got my hands on a 3890 from ZF and ran into several issues right out of the box. The hour indicator on the chrono was constantly running, even when the chrono was stopped and tachymeter hands would not center at 12 for the love of gods. I sent it back for servicing with the dealer and when I got it back, the seconds hand at 6 was stuck.
That in combination with the added thickness compared to the gen led to a serious discussion about getting a refund, which was agreed with the dealer as the movement was indeed faulty.
I am now on the market for a 3891, and if you find a TD with one in stock, do let me know as well. XD