Last slave in line does not insert sercos address in CP0 AT frame in 511 slave configuration

Connected 63 nxio 100 (multi slave firmware x8) and cifX (x7) as last to a line.

In CP0 AT frame number of slaves is 511 as expected.
Last 7 slave addresses (from cifX) are not in AT frame.

After closing the ring all slave addresses are in AT frame.