This story happened just a year ago. I was in Oman in Buraimi to be exact, waiting for my employment visa. I meet new friends because of that others are also waiting for their visa as well. We were 8 in a room, our room have it's own kitchen, a receiving area and one bathroom.
3 of my room mates went outside together with other people from the other room to eat outside, they were inviting us but we were so lazy to go outside and we already ate our dinner, we were playing cards while the eldest in our group went inside the room to put clothes since she just finished her shower. She went outside again with us in the living room. She closed the door so that the ac can cool the room fast. We are still playing cards and decided to go outside to grab snacks (well if you are an exiter, you will just eat all day every minute, every hour.) The youngest tried to open the door but it was locked.
"Did you locked the door?" Yael asked Hana.
"No, why would I locked it?" she stood up and went to the door but it was locked then we heard a loud noise from inside of the room as if someone throw something, we all ran outside the room which caught the attention of the people who are in the stairs. They asked us what happened and we told them that the door was locked and we heard something. We reported it to the receptionist but he just laugh at us then he unlocked it and says that maybe the wind locked it and the sound that we heard were maybe from the other room. Given that the sound was from the other room but how can hana locked the door? The door could only be locked by a key from inside which we doesn't have and there's no wind to closed the door because the window was tightly closed. After that incident strange things happened.
I was the one who is cleaning the dishes when I saw a reflection of a black human form walking and I wan towards my roommate who are watching T.V. It's impossible that it's my shadow because it's walking from left to right and It's not even my reflection because I was wearing blue at that time.
There's also this one incident that we are all eating our lunch while we are watching T.V I looked to Yael that time and in my peripheral vision I saw a hand reaching on Dennis' back but I ignored it thinking that maybe it's just my imagination but the ac suddenly turned off and we all asked Dennis if he turned off the ac since the switch is near to him. He told us that he didn't turned it off because his hands were full (of plates and spoon). And I think that what I've seen was not my imagination, that thing turned off the ac. They all joked at me saying that maybe the ghost doesn't want too much cold in the room, (I always switching on the ac because I feel so hot every time.) But in reality ghosts wants cold room or cold environment.
And thankfully, there's a little chance of me going back there and hopefully that little chance becomes 0% chance. I really don't want to go back there.
I'm in agreement with RC's assessment of the air conditioning unit having a thermostat as a likely explanation for that specific experience. Also, some electronic devices have built-in safety sensors to make them stop working for a while; this rest is necessary for the motor can cool down to prevent the device from bursting into flames. However, for the rest of my thoughts, I'm going to include your statement that you thought you saw a hand reaching behind Dennis as a factual point in the experience.
As an immigrant to the U.S., I know that Government Bureaucracy can be incredibly slow-moving, sometimes can require really strange information, and can put very strict limits on the person waiting for the over-worked Government employees to double-check massive piles of paperwork (even though you've done all the paperwork correctly). My thought about your living situation at that time is that people waiting for work visas, entry visas, etc., can become anxious, stressed, even panicked about how long the process takes. If there is an entity haunting that location, it would have a lot of people's emotions bombarding it regularly. The energy such spirits seem to need to take from people so they may interact with the living would be available in plentiful supply; it wouldn't necessarily want to scare anyone because it is already being "fed" those emotions without trying to cause them.
I'm raising this point about the entity/spirit *NOT* deliberately scaring anyone is to support your title "Extra Roommate." Everything that the entity seems to have done in your narrative is much more in keeping with the behavior of someone who believes himself/herself to be living there: "That door should not be unlocked!" "I wonder if I left my book near the television?" "Excuse me, Dennis, I'm getting chilly." These hypothetical examples perfectly normal behavior for a living person, but unsettling to everyone else who knows that a living person is not there. Perhaps he or she imagines that the other inhabitants are just the "new arrivals" in the apartment, and you happened to be the person who reacted oddly every time he/she did something perfectly ordinary.
Thanks for sharing this narrative with us.
Best,
Biblio.