antpool minutely hashrate looks like a comb, is this normal?

[chapsmx]

hi guys.

yesterday i received a couple hasbords, which were sent to warranty to bitmain, so plugged the asic and after 24 hour without hw errors im getting the following hashrate chart, which i think is not normal but what do you think?

chart by minutes
https://i.imgur.com/Dx30uIw.jpg

miner status
https://i.imgur.com/dFOOd6h.jpg

any input would be highly appreciated!

greetings.