Living with a TL-WR842ND (sysupgrade bricks router)

I think there might be a bug somewhere. I've just noticed that sys% usage is ridiculous when everything goes to hell.

  >pppoe-wan                    │ 494.90KiB    351 pps     │  12.13KiB    192 pps

Mem: 19620K used, 8308K free, 4K shrd, 864K buff, 1472K cached
CPU:   1% usr  93% sys   0% nic   0% idle   0% io   0% irq   4% sirq
Load average: 6.89 4.88 2.96 5/58 9906
  PID  PPID USER     STAT   VSZ %VSZ %CPU COMMAND
 1555     1 root     R     1948   7%  16% /usr/sbin/hostapd -s -P /var/run/wifi
   97     2 root     SW       0   0%  12% [kworker/0:1]
  440     1 root     S     1180   4%   7% /sbin/ubusd
 9165  8584 root     R     1196   4%   5% top -d3
  840     1 root     S     1396   5%   5% /usr/sbin/odhcpd
 9886  9883 root     R     1224   4%   4% /bin/sh /etc/netCheck.sh
    3     2 root     SW       0   0%   4% [ksoftirqd/0]
  104     2 root     SW       0   0%   2% [kswapd0]

Mem: 21212K used, 6716K free, 12K shrd, 792K buff, 1584K cached
CPU:   6% usr  88% sys   0% nic   0% idle   0% io   0% irq   5% sirq
Load average: 3.38 2.13 1.16 1/56 9259
  PID  PPID USER     STAT   VSZ %VSZ %CPU COMMAND
   97     2 root     RW       0   0%  18% [kworker/0:1]
 1555     1 root     S     1948   7%  12% /usr/sbin/hostapd -s -P /var/run/wifi
 2714  2713 root     R     2484   9%   4% /usr/sbin/bmon -p ppp*
 9240  9239 root     S     1184   4%   4% /bin/ping -W 3 -c 6 -q -I pppoe-wan g
  840     1 root     S     1396   5%   4% /usr/sbin/odhcpd
    3     2 root     SW       0   0%   4% [ksoftirqd/0]
 9241  9239 root     S     1204   4%   3% awk /packets received  {print $4}
 9165  8584 root     R     1188   4%   3% top -d3
 2389     1 dnsmasq  S     1412   5%   2% /usr/sbin/dnsmasq -C /var/etc/dnsmasq

Vs. my WDR4300

 >pppoe-wan                    │ 420.29KiB   1.69K pps    │  78.09KiB 1.10K pps

Mem: 42960K used, 17456K free, 216K shrd, 3084K buff, 9716K cached
CPU:   5% usr   1% sys   0% nic  79% idle   0% io   0% irq  14% sirq
Load average: 0.14 0.13 0.13 1/59 7749
  PID  PPID USER     STAT   VSZ %VSZ %CPU COMMAND
 2365     1 nobody   R     5260   9%   4% /usr/sbin/darkstat --verbose -i br-la
 2297  2295 root     S     2408   4%   3% /usr/sbin/bmon -p ppp*
    3     2 root     RW       0   0%   1% [ksoftirqd/0]
 2548  2536 root     R     1188   2%   1% top -d3
 2229   995 root     S     1132   2%   0% /usr/sbin/dropbear -F -P /var/run/dro
20388     2 root     SW       0   0%   0% [kworker/0:0]