Breadboard ATmega328P@internal8MHz upload verification fails
I'm not familiar with Platform IO but since you are telling that setting a lower CLK helps, you can adjust your settings file to add option for avrdude to always program at wanted CLK speed. Check this URL for instructions: https://docs.platformio.org/en/latest/platforms/atmelavr.html#upload-using-programmer

Probably (just a guess, didn't checked that) default settings are adjusted for 16 MHz settings which is the most widespread with ATMega328p boards and especially Arduino's.

Another URL with similar error which might help is: https://community.platformio.org/t/atmega328-internal-clock/6236/4