I have a similar laptop (TUF Gaming FX505DY), and the very same problem, with
kernel 5.3.7 and governor set to 'performance'.

When I run a game with DRI_PRIME=1 (to use the dedicated GPU) the system gets
throttled down at some point and never recovers. Every CPU core runs at 400Mhz
which makes the system practically unusable until reboot.