Some guidance now on cxagents.com:
Code:
E-Ticket Coupon Should Not Exceed 16 Coupons
According to IATA standard, the maximum number of conjunction tickets is 4,
which is equivalent to 16 coupons. ET exceed this limit may cause problems at
check-in and subsequent update actions. Please issue paper ticket instead to
avoid causing passenger inconvenience.
So obviously this is quite a common problem.