It happens in any town. Also ED-E can't carry faction armor.
Yea... heres a big list of bugs connected to just ED-E
■Completing the quest ED-E My Love by giving him to the Followers may result in him teleporting to a location near red rock canyon(shown by quest marker) and then exploding on approach, removing him from the game as a companion.needs verification
■It would seem if you bring ED-E into the White Glove Society's kitchen, he will stop moving and just float in place. You can still interact with him, but he will not follow you. This can be avoided by telling him to wait outside the kitchen area and then going back to get him after you're done in there.
■When told to stay, he can appear to you soon after even though you clearly told it to wait there.
■After rescuing Primm's deputy all Primm citizens may became hostile to ED-E.
■After chatting to the commanding officer at Ranger Station Charlie, the officer may become hostile to ED-E
■The Legion members inside Cottonwood HQ may become hostile to ED-E at random.
■NCR troops at Camp McCarran may become hostile to ED-E at random.
■Completing the quest "ED-E My Love" by giving him to the Brotherhood may result in ED-E no longer moving or shooting anybody. It will still fast travel with you and zone with you, but will stay where you spawn. Changing him from follow to stay, and then back to follow fixes this problem, but he still won't attack enemies. Also reported to happen if you side with the Followers of the Apocalypse at the end.
■Giving ED-E a suit of Brotherhood T-51b power armor to hold onto will result in the armor disappearing from ED-E's inventory with no way to retrieve it or he will drop it.
■When completing the quest ED-E My Love, you're given a chance to upgrade the robot either by giving him to the Brotherhood of Steel, or the Followers. To achieve this upgrade, the entity is swapped out with an entirely different base ID, without making the inventory persistent. The effect of which is destroying any items in ED-E's inventory.
■Sometimes ED-E may be randomly attacked if the player interacts with people.
■To fix this issue on the PC, you can spawn the standard ED-E at your location using the console. Take your belongings from it, then destroy the temporarily spawned entity.
■When trying to pass under the floor of BoS underground base in hidden valley, ED-E may get stuck in the low floor when trying to follow you.
■While entering vault 34 ED-E may get stuck and leave your party and return to primm. When you return to primm, ED-E will begin to attack you with no chance of stopping the attacks. (360)
■Having ED-E wait anywhere until he returns to Primm may result in him becoming hostile to everyone, including your character. You may be able to retrieve your gear from him by pickpocketing.
■ED-E will disappear if you enter the Lucky 38 Casino. But cannot recruit Rex as It appears ED-E is still following you.
■ED-E will completely disappear and will not be at Primm or the Lucky 38. (360)
■Several staircases (with roofs/walkway covers) can cause ED-E to become immobile and/or phase through the bottom of the level (Confirmed PS3)
Didn't see the need to add them all to my list unless ppl are saying they're experiencing it now because I have no clue how out of date some of those are. Yours is already on the list "generalized" as Companions iniating combat with non hostile targets because other companions are doing it as well.