Are you changing the Z offset in the config.h or in the eeprom.
Values in eeprom will always have precedence over the values in config
In the latter case where you update the config.h and upload the firware, you need to send a M502 followed by M500 to update the eeprom values.
Values in eeprom will always have precedence over the values in config
In the latter case where you update the config.h and upload the firware, you need to send a M502 followed by M500 to update the eeprom values.