The `; first_layer_bed_temperature` and `; first_layer_temperature` compatibility lines were always taken from filament 1. Anycubic's GoKlipper reads the bed line to heat the bed, so a plate printed only with another filament got the wrong temperature.
The bed line now follows `bed_temperature_formula` (highest used filament or first printing filament). The nozzle line uses the first printing filament. Both values are computed before the by-object loop.