Right now I have the problem again. The signal is otherwise good:
wlp3s0 IEEE 802.11 ESSID:"kerberos"
Mode:Managed Frequency:2.452 GHz Access Point: E4:3E:D7:3B:FB:C3
Bit Rate=144.4 Mb/s Tx-Power=22 dBm
Retry short limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=67/70 Signal level=-43 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0