I have 3 different Roku products and all of them are slightly different. None of them have a back that stays on. The back always falls off. Always. At my friends house her Roku remote back is always lost too. When will the Roku remotes get updated to have a more secure backing?
Usually its very hard to get the battery door off initially, if yours is falling off easy, it must been broken at some time? Do they still have little tab on them? I do not think roku sells battery doors. I have many roku remotes go through my hands and never had one where the battery door wouldn't stay on. I bought broken remotes that turned out to really be broken, and I purchase at least 4 that were missing battery doors, in the end they match up. The battery door for rc-al2 remote will fit securely on a rc-al4 remote, but with an under bite.