Not a bad idea to name your dimension styles explicitly, I've found, and to never, but never use a style named "Standard" (said style being "vicitimized" by several s/w out there--or acting like it).
So, for a floor plan at 1/8", I just start a DimStyle called Plan96, and use that. What I _try_ to do, is to keep a current 'dummy' style up after I get most of the dimensions in place. That way, if anything 'monkeys' with the dimstyle, it only changes the "dummy" and none of the current dimensions.
Now, if you see a discombobulated dimesion, go to DDIM and looks to see if the dread asterisk is up there, showing an unsaved Style change. Having a good Style to flip to can be a cool save. How so? Well, ACAD will ask "Save Changes to [dimstyle]?" Just say "No." This will (often) Undo whatever changed.