have you try to set :
-eres Allocate DAG buffers big enough for n epochs ahead (default: 2) to
      avoid allocating new buffers on each DAG epoch switch, which should improve DAG switch stability

or with luck :

-lidag Slow down DAG generation to avoid crashes when swiching DAG epochs
      (0-3, default: 0 - fastest, 3 - slowest). This option works only on AMD cards

here i have remove " -minspeed "

because Nanopool made me minning sometime slowly ( 60 mhs )
but the miner ( black line on nanopool ) work @ 150 mhs ....

and rig have free reboot for nothing ....