Flight Attendant reported right after takeoff the door operating handle at 4 left popped up from the closed position and it was difficult to close. They communicated with the pilot and decided to continue the flight; but upon landing the door handle moved towards the open position. They were able to close the handle and disarm the escape slide preventing an inadvertent slide deployment.

Narrative

Right after takeoff; the door operating handle at door 4L popped up from the fully closed position. The other AFT FA and I immediately noticed and on instinct I immediately told her to pull it down. They said they felt resistance as if it was going to pop open and we agreed to call the pilots. The other aft FA called them and they asked us some questions and had us release the handle and it immediately popped up several inches but didn't go any further. They had us try pushing it down really hard to see if it would stay closed which also didn't work. They had the other aft FA take videos and photos to document it and go to the front to show them. During this time I did not feel comfortable and was worried the door could fail so I remained seated with my seat belt fastened fully. A bit later my colleague returned to the back and told me the pilots were talking to dispatch and maintenance to decide what to do. After a bit the pilots called us to say they thought we were okay but asked our comfort level. I said I would be comfortable if the dispatch and maintenance teams said it was safe to continue. The rest of the flight we were extremely cautious of the door and kept a close eye on it. Neither of us were comfortable sitting next to the door for landing so we both occupied the 4R jumpseat. During landing when we were close to the ground (maybe during the last 30 seconds) the door handle lifted up to almost the window of the door (about a quarter of its total range of motion). We were extremely afraid the door would open fully possibly causing an ISD (Inadvertent Slide Deployment) or a more severe emergency. We could hear the engines and reverse thrust extremely loudly and our ears were ringing after because of the noise level. We could also see light coming in around the door seam. Once we had slowed down and began to taxi to the gate; we called the pilots and they told us to immediately disarm the door. We tried but it wouldn't disarm so we pushed the operating handle back to the closed position and then immediately disarmed the door. We both agreed after that this situation was the most scared we've ever been while flying and we felt like it was very close to having an ISD or an even worse emergency. I puked in the bathroom during deplaning (I believe from adrenaline) and was shaky until we made it to the hotel. Personally in the future I don't think this decision should be left up to crew comfort and instead believe a situation like this should always be treated as extremely important and dangerous. I also believe we should have a standardized SOP for how it should be handled. I also don't believe we should have continued to fly for hours over the ocean with a faulty door. Personally I greatly appreciated the way our pilots handled the situation and greatly appreciated that they check in with us multiple times throughout the flight. I think to improve for future situations it would be nice to have a briefing between the pilots and flights attendant before the top of descent to outline expectations for how we will handle situations like this during the descent. Myself and the other flight attendants agreed we wanted to clean up early to be seated as the plane descended in case the pressure decreasing during descent caused the door to come loose. We also agreed for both myself and the other aft flight attendant to occupy the jumpseat at 4R rather than 4L due to the 4L jumpseat proximity to the problematic door. Having a briefing would help us to understand exactly what our duties are regarding the situation and make sure that we are doing the safest thing possible in the future. Overall I believe it should be treated as an emergency going forward.