There doesn't seem to be any legit way of fixing this. I tinkered with the pressure sensors and valves, kicked the pressure cooker a few times, still the E4 error presented itself.
I was able to bypass the E4 error by completely bypassing the electronics and wiring the heater coil to get power whenever the pressure cooker is plugged in. It was a very simple job, anyone with any electrical experience can do this.
The only problem is that it is a safety concern as there is no way for the heater to turn off even if pressure is getting to be way too high. There may be a pressure relief valve in the lid but the heater coil won't shut off, so don't leave it unattended! But at least this way to you can still pressure cook.
Pics of process:
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Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them