Thank you both for the reply!
I found and exluded the offending VLAN. The connection type is now L2 and AirWave is reporting hitless failover as possible.
Before:
(bmh-ep01-wlc-02) [MDC] #show lc-cluster vlan-probe status
Cluster VLAN Probe Status
-------------------------
Type IPv4 Address REQ-SENT REQ-FAIL ACK-SENT ACK-FAIL REQ-RCVD ACK-RCVD VLAN_FAIL CONN-TYPE START/STOP
---- --------------- -------- -------- -------- -------- -------- -------- --------- --------- ----------
peer 10.134.127.21 157 0 91 0 91 79 1108 L3 Conn 8/ 19
After:
(bmh-ep01-wlc-02) [MDC] #show lc-cluster vlan-probe status
Cluster VLAN Probe Status
-------------------------
Type IPv4 Address REQ-SENT REQ-FAIL ACK-SENT ACK-FAIL REQ-RCVD ACK-RCVD VLAN_FAIL CONN-TYPE START/STOP
---- --------------- -------- -------- -------- -------- -------- -------- --------- --------- ----------
peer 10.134.127.21 193 0 129 0 129 115 0 L2 Conn 18/ 18