Solution:

Customer could not get an X-Ring to work when wireless bridges were placed between the managed switches involved in the ring. A X-Ring topology is maintained by BPDU of X-ring protocol and X-ring BPDU packets just can be produced from X-ring port . If you connected a wireless AP to X-ring ports between two switches, then you would loss the Redundant Ring capability, because switches couldn't exchange the BPDU from each other to maintain this Ring topology. I found the below reference on the web to BPDU. Bridge Protocol Data Units (BPDUs) is used by bridges in a network to exchange information regarding their status. The Spanning-Tree Protocol uses the BPDU information to elect the root switch and root port for the switched network, as well as the root port and designated port for each switched segment. The program in each bridge that allows it to determine how to use the protocol is known as the spanning tree algorithm, which is specifically constructed to avoid bridge loops. The algorithm is responsible for a bridge using only the most efficient path when faced with multiple paths. If the best path fails, the algorithm recalculates the network and finds the next best route.