It's not just you. In general, each map has its "disarm dificulty level" - (almost) all locks on the map require Disarm Traps at this level at least. Haunted Mansions have 26, Harmondale(!) has more than 20 and so on. Levels over 20 are completely normal, the highest level have Colony Zod and Lincoln. The highest disarm difficulty level possible is 40.Therefore, M7 does not suffice. Haunted Mansions need M9, for example. What to do? You need a very good item of Disarming, preferably +20 or better. You can get one from the EI Dragon or any other Dragon or Blood Titan. You can buy an item of Disarming +17 in Deyja or in Bracada Desert. Your M7 with an item +17 will have Disarm Traps 38 so that he will open almost all locks in the game.
