System reset/fatal error

Any ideas what causes this?

02/20/2016 : 22:17:36 CET : : Rf Core : Invalid NiBuf:2486000 Hdr:9e67 on Q:3fa2e4 Src:3 SrcIF:3 Dst:20087 Alc:36449 Len:70 Cop:65
02/20/2016 : 22:17:36 CET : : Rf Core : Buffer:

AllocLUID 36449
BufLen 70
CpyCnt 65
DstLUID 20087
MsgType 1
NiBufSignature x9e67
SrcAP 0
RtIF 161
SrcIF 3
SrcLUID 3
Rcvd RSSI 37 V 35 H
VLAN VID 1

00228334 18032A00 3EA016F2 08004500 00346B3A 40004006 DC3AC301 14794A7D
D1572F0F 01BB2C69 681F7F6D 0B9E8010 1000E6EF 00000101 080A2098 0D0484E4
899FA321 CF9570B1 C506880F 89A0E670 0CD3630F 82838E94 4DFEBA21 3F1F7FB9
1BD44F2B 016FAF8F CAC42579 49B18C38 90352B1F 6B41AFF0 18460003 81000001
F8DB277A FC8188DE 01B5C502 435DD1F5 2FB15CDA A43AD8C2 E6519C7E C0235D8A
329CC969 B0C2373C 57B0B3A2 F205137B 6D4512D9 59961C18 15309334 CAA0A810
85FBA27F 70545FA8 366D801D 1210A2BA C5AB1E45 C0E1E124 49390C19 A02665F7
42CC5AB9 B759D0C1 C4748FD2 4D73B25A 0B742F19 AE8DE7F0 D9C52AC2 89E1D3F2

:Rf Core: FatalError()
Stack Dump information:
Current Stack size: 692 bytes
Stack Dump:
0x14031d4c: 024f986c 0000005a 000002ac 00000003
0x14031d5c: 000002b4 14031d68 00150e38 003091f8
0x14031d6c: 000001f9 024f9800 0000006b 14020070
0x14031d7c: 00000001 14031da0 14031d8c 00150f1c
0x14031d8c: 003091f8 000001f9 00000001 00000001
0x14031d9c: 00000001 00043940 00009e67 003fa2e4
0x14031dac: 00000003 00000003 00004e77 00008e61
0x14031dbc: 00000046 00000041 00000001 14020050
0x14031dcc: 00000000 0097f8bc 70001114 00000001
0x14031ddc: 70001010 00000004 14031e30 14031e28
0x14031dec: 0066b854 02486000 700010d8 00043ba0
0x14031dfc: 00000001 70001114 14031e28 007cfe9c
0x14031e0c: 02486000 00045644 02486006 02486000
0x14031e1c: 00000000 02486000 00044214 00005000
0x14031e2c: 06dd06d8 2d200313 00000013 0000000b
0x14031e3c: 00000000 14020134 1402012c 14020124
0x14031e4c: 1402011c deadbeef 00000988 00000001
0x14031e5c: 0000000f 14031ed4 000001e4 00000000
0x14031e6c: 00000020 00000020 00000020 00000005
0x14031e7c:
01/01/2011 : 01:00:00 CET : : Bridge Core :
01/01/2011 : 00:00:00 UTC : : Bridge Core : Time Set
01/01/2011 : 01:00:00 CET : Bridge Core :
******System Startup******
System Reset Exception -- Watchdog Reset
Software Version : CANOPY 13.1.2 AP-DES
Board Type : P12
Device Setting : 5.7GHz MIMO OFDM - Access Point - 0a-00-3e-a0-15-38 - 5630.0 MHz - 20.0 MHz - 1/16 - CC 11
FPGA Version : 011514
FPGA Features : DES, Sched, US/ETSI;
01/01/2011 : 01:00:17 CET : Bridge Core : Acquired sync pulse from Power Port.

Hi - I noticed you are still running 13.1.2.  I would highly recommend moving up to 13.2.1 at least.  It is a very stable release and widely adopted.  There were a large number of performance improvements in that release.  One in particular that is related to your log is that the AP has a different CPU archictecture., so there is no longer an "RF Core".