There was a known issue with the electrical maintenance door opening when it shouldn't that had been fixed in the past, but it turns out there was more than one thing causing conflicts with this door.

If you have unlocked the door to the sub-reactor in your playthrough, there is a glitch that will cause the electrical maintenance door to be unlocked once you save and reload the game. This is not intended, this door should not open under these circumstances, and it will no longer do so.

The electrical maintenance keys are tied to an important scripted event that will not occur if you do not pick them up.

Please note that this does not constitue a softlock, the game CAN progress normally even after this, so there is no need to restart your playthrough, HOWEVER: you will miss out on a large quantity of content by doing so. This also means that the sub-reactor door will be locked again, as this was an issue with the save system, meaning that when the sub-reactor will be available to explore completely in the future, you will not be able to do so.

If you have already shut off the power and don't wish to restart your playthrough, it is possible to still acquire the keys after the lights are off and go through the scripted event.

I apologize for this, this is a result of my past inexperience with the saving system that slipped through the cracks. It's normal to have glitches that need fixing at launch but this one in particular is a major one that should not have made it to the final product.