Prius 2016,Gen4 going downhill battery overcharged and blocked

Hello guys, can i ask you if my issue is something to worry about or not.
I drive a 2016 Prius Gen4 with 40 000 miles on it. Today i drove downhill for 7 miles without using "B" mode (i know this is my mistake). Battery charged on the first mile and then i drove with the engine braking which i know is normal. However when i got downhill and started to use my regular battery i managed to discharg it to 10% and my engine breaking was still going. Meaning my engine wasn't charging the battery as it used to do.
What i did was to cool the engine, shut it off, let it rest, started driving carefully and the battery charged to 40% which is normal.
I checked with OBD scan tool for errors and i couldn't find any. There were no errors, engine is runnig cool, i have regular maintenance and everything.
Please tell me if i should worry because my warranty just expired
Thank you in advance. I appreciate any help.

 

I recently cleaned the air filter for the battery fan, i got really scared because i was travelling with my 2 year old son in a mountain area. Perhaps indeed the battery overheated and this was prevention to avoid any damage. I would really appreciate if Toyota put some warning labels for these kind of situations as i coudn't find any in the manual. I will drive it today and post my results, i think this issue may happen to other people. Thank you guys.

 

The problem with me is my car is bought from and auction in California and it was salvage title (back bumper and taillights were not working,everything else is brand new) so for me there is no warranty, so i try to check if everything is ok with the car. So far there is no problem with car when i am driving on regular road, but i will take it to the dealer for oil change and bring the matter and tell you what they think.