Got adjusting fuel pressure regulator, keeps requiring adjustment (temp related?)

I got a fuel pressure regulator from CosmosRacing, non AEM unit with gauge and when I set it to 3.5 bars in instance 1, drive around, shut off the car, drive around more etc.

Start the car and check the pressure gauge and it would show 4 bars, etc. It does not stay pre-set at 3.5.

Is this normal for fuel pressure to be off in adjusting regulators for colr starts/based on weather temp? Or should I get an AEM one?