As simple as it sounds.
If you have a Fortnite door and you place a Door Lock Device on it, it will no longer work in game and the player won’t be able to Open or Close it.
I’ve tried Locking and Unlocking it with no luck, starting Open, starting Closed.
Nothing 
yeah I have been having the same issues, deleting the lock and door and replacing them with the same objects works but only for 1 start game cycle in my case. very annoying
Bumping this, happened to me too. Had to restart UEFN for it to happen.
@Rynex_FNC Thank you for your report! We would like to look into this further, would you be able to submit a bug report using the form available here? Fortnite Creative
Hey Stevie,
Apologies for my late response, I just submitted the bug report.
Thank you!
I did some experimentation with this. If you set up the locks etc. in the old Creative Editor it will work as expected. But only until the next time you sync changes from UEFN, when it will revert to the error state. The changes DO NOT even have to be related to the actors in question. Hope this helps.
I am having issues with this, I had this working a month or two ago but on new maps I can’t get door locks to work at all - I get the visual cue in the UEFN editor its bound to a door but at runtime nothing happens
@BPANDREW Thank you for your report! We would like to look into this further, would you be able to submit a bug report using the form available here? Fortnite Creative
I too have a lock device for one of the holodeck programs. I think it worked well (see 3039-4145-5931)
I have an automatic door, so I wait for all players to leave the area near the door before locking.
Also, I only lock for one agent, not for each.
I am away from PC, but I can share my door/device settings later if needed or on discord.
The status of UCB-1127 incident has been moved from ‘Awaiting Validation’ to ‘Closed’.
The bug seems to be still persistent in UEFN.
Even if the Lock Device confirms proper positioning, Starts Locked (Locked / Unlocked) or Initial Door Position (Open / Closed) different values do not seem to influence the door to which it’s attached.
Are you saying that by restarting UEFN the functions configured on the Lock Device starter working?
Tested at my side but they’re still not.
Bumping this.
Still experiencing it, even after the 28.20 Release.
Bumping this, seems this is still happening in 29.10 release.
Bumping this as I still cannot get it to work.
My whole map is bugged and based on locking and opening doors. What worked before is suddenly completely broken. Tried to debug or figure out why. No clue.
EDIT: I tried the unlocked setting first, changed them to sliding doors, the memoty increased with about 4000 points. Suddenly the first time it worked., but now it won’t open a second time, even though the interact button sais “open”.
It also does not matter if you “attach” the door to the lock.
Bumping… It works if i restart UEFN, but after any changes stops working again