ASUS RT-AC51 looses internet connection

[johannes_i_gbg]

The router connected to the connection box where the fiber comes in, looses connection to internet now and again. WIFI is still strong but all units connected shows the message "no internet connection"

Logfile from the router interface below when it last lost connection. Any ideas?

Sep 2 09:12:23 kernel: APChkCls2Cls3Err():Rx a frame from 34:e1:2d:88:d1:19 with WCID(255) > 75
Sep 2 09:12:23 kernel: APChkCls2Cls3Err():Rx a frame from 34:e1:2d:88:d1:19 with WCID(255) > 75
Sep 2 09:12:23 kernel: APChkCls2Cls3Err():Rx a frame from 34:e1:2d:88:d1:19 with WCID(255) > 75
Sep 2 09:12:23 kernel: PeerAssocReqSanity - IE_HT_CAP
Sep 2 09:12:23 kernel: PeerAssocReqSanity - IE_EXT_CAPABILITY!
Sep 2 09:12:24 kernel: Rcv Wcid(2) AddBAReq
Sep 2 09:12:24 kernel: Start Seq = 00000095
Sep 2 09:14:15 kernel: Rcv Wcid(4) AddBAReq
Sep 2 09:14:15 kernel: Start Seq = 000001ad
Sep 2 09:15:16 kernel: Rcv Wcid(4) AddBAReq
Sep 2 09:15:16 kernel: Start Seq = 000001cc
Sep 2 09:15:42 kernel: Rcv Wcid(4) AddBAReq
Sep 2 09:15:42 kernel: Start Seq = 000001e4
Sep 2 09:15:46 kernel: Rcv Wcid(4) AddBAReq
Sep 2 09:15:46 kernel: Start Seq = 000001f0
Sep 2 09:21:50 kernel: Rcv Wcid(4) AddBAReq
Sep 2 09:21:50 kernel: Start Seq = 0000055e
Sep 2 09:26:47 kernel: ageout 8c:45:00:aa:e3:3e after 300-sec silence
Sep 2 09:26:47 kernel: Send DEAUTH - Reason = 3 frame TO 8c 45 0 aa e3 3e
Sep 2 09:33:13 kernel: APChkCls2Cls3Err():Rx a frame from 8c:45:00:aa:e3:3e with WCID(255) > 75
Sep 2 09:33:13 kernel: APChkCls2Cls3Err():Rx a frame from 8c:45:00:aa:e3:3e with WCID(255) > 75