Are you using EAP TLS?
Can you check MTU size in show tech. Its under the command "show datapath bridge":
# show datapath bridge
Datapath Bridge Devices
-----------------------------
Flags: F - source-filter, T - trusted, Q - tagged, I - IP
S - split-tunnel, B - bridge, M - mesh, P - PPPoE
C - content-filter, O - corp-access, h - to HAP, f - to FAP
h - dhcp-redirect b - blocked by STP
Dev Name VLANs PVID ACLs MTU FramesRx FramesTx Flags
--- ------------------------ ----- ---- ----------- ----- -------- -------- --------
3 eth1 1 3333 134/0 0 1500 0 95 FB
8 bond0 3 1 0/0 106 1500 992430 476608 FTQB
12 gre0 1 0 0/0 0 1500 4107 1106 FTQB
15 br0 0 1 105/0 0 1300 374780 0 IB
18 aruba000 1 168 109/0 0 1500 1135 2043 B
19 aruba100 1 168 109/0 0 1500 0 921 B
20 aruba001 1 166 110/0 0 1500 5669 5079 B
21 aruba101 1 166 110/0 0 1500 63572 55628 B