putty with ClientAliveInterval keepalive packets?

• server : sshd installed on centos 8 with ClientAliveInterval=5 and ClientAliveCountMax=1
• client : putty on win 10 (with reverse tunnel of local port 5000 to server port 6000)

putty keeps append these lines to its log file every 5 seconds, what does it mean (especially SSH2_MSG_CHANNEL_FAILURE)?
I expected to receive keep-alive from server and send acknowledgement to it!

Incoming raw data at 2020-07-23 09:47:11
  00000000  02 6a 4f 7d 02 01 bd bc 76 c6 49 10 fa 37 72 b1  .jO}....v.I..7r.
  00000010  2e 44 e3 12 86 5c aa c7 d7 34 6f 10 ab 26 0c e0  .D......4o..&..
  00000020  47 8d 1a a9 87 1a 26 1a f3 fa 5a c9 37 e4 1a d5  G.....&...Z.7...
  00000030  ef 29 e4 48 ce 4b 0b 6c 91 3d 9c fe de d0 41 70  .).H.K.l.=....Ap
  00000040  7e 2c 84 5a c2 eb b3 96 2a cb 93 64 34 44 5f 2f  ~,.Z....*..d4D_/
Incoming packet #0x19, type 98 / 0x62 (SSH2_MSG_CHANNEL_REQUEST)
  00000000  00 00 01 00 00 00 00 15 6b 65 65 70 61 6c 69 76  ........keepaliv
  00000010  65 40 6f 70 65 6e 73 73 68 2e 63 6f 6d 01        [email protected].
Outgoing packet #0x15, type 100 / 0x64 (SSH2_MSG_CHANNEL_FAILURE)
  00000000  00 00 00 02                                      ....
Outgoing raw data at 2020-07-23 09:47:11
  00000000  97 5a 22 89 78 32 54 52 56 48 ce b5 f6 14 2a c3  .Z".x2TRVH....*.
  00000010  7f 3a 94 90 f5 0b 29 c7 e8 40 21 57 ce 60 ee 73  .:....)..@!W.`.s
  00000020  71 6e c2 c8 80 c6 ab b9 a7 87 d6 f5 5a 37 ed 24  qn..........Z7.$