Bug with Scale Mail and (DEX?) Ability Checks

In Caer Lem, in the area with the brimstone viper fight, my Ranger wearing Scale Mail has disadvantage on "disarming" the falling plank traps. I'm not sure why this would be, since the more cumbersome armors are only supposed to give disadvantage on stealth checks, not all other DEX-related checks, but the advantage/disadvantage popup I get when hovering over the disadvantage text does note that it's due to the Scale Mail. I removed the Scale Mail from my ranger to disarm another falling plank, and she rolled normally, with no disadvantage.