Unusual Desired Altitude during take-off

Hi,

For the last couple of weeks, I have observed that my drone takes off rather slowly for the first time. After the first flight, it behaves normally (which means it takes off at the desired velocity).

Unusual behaviour logs:
https://drive.google.com/file/d/198hYxI7a_be5mkHPRHO_UJSaDrftZ9ll/view?usp=sharing
https://drive.google.com/file/d/1-vyjmi5bazkc7ryrgb4JoeGnz_Bxn74i/view?usp=sharing

Normal takeoff logs:
https://drive.google.com/file/d/1ADeuNZbsrkq3oQJ665CdEOxcfJDfZ_tP/view?usp=sharing

For unusal behaviour, I have observed in the log that there is a sharp dip in the Desired Altitude .
But this behaviour is observed only on the first flight of the day. Even if I restart the drone or completely power-off and power-on, then also I can not reproduce it.

Can anybody explain this?