If you have some features that look fine in the viewport, but they disappear or act weird when you hit play, or render with MRQ, then those actors might be on a sublevel that is set to the level blueprint streaming method.
You can check if you go to Window > Levels. See if Persistent level has any sublevels under it. If any have a blue dot next to the name, they are set to Level Blueprint Streaming. You can right click the level name in that menu, go to “Change Streaming Method” and set it to “Always Loaded”.
Do those actors have “Hidden in Game” on them turned on? I’m not really sure what else could be causing this unfortunately. Try scrolling through the details on those missing Actors and look for attributes that have been edited (there will be a little u-turn arrow to the right of them). Compare them with ones that are visible in the render and see if you can spot any differences.
@EvanHammel - I checked all attributes of the actors that appeared in the render and those that were not and they were identical, BUT this actual lead me to consider the logic that I have done so far in the level blueprint and once I disconnected EventBeginPlay, the actors appeared again, so I guess the logic for OnActorBeginOverlap (which would toggle the actor hidden in the game attribute) would affect the visibility in the render; anyway I’m glad I found the root cause and thank you for your support