You have enable gravity on correct? Even if you have simulate physics unchecked it will still use that for the actual breaking simulation.
While I haven’t used it a whole lot, that’s the only things I’ve found that I know would cause that type of issue other than setting mass scale values or such too low but it looks like you already checked those.
Less likely is what is your scale of stuff at? If you make a block and drop it it falls like it should if set to simulate? I had a massive mech smashing through walls and with the scale really high even with gravity everything fell really slowly, so while not likely it’s also something that comes to mind in case you just imported a new mesh/character but it’s scale was off and didn’t have anything else in your test scene to compare it to and so didn’t notice.
Otherwise have you tried creating a new destructible object without touching any settings to see if you still get this result? If so then try setting it to break on collision and just walk into it to see if it’s something specific to your weapon or sword swing. Also creating one in a new level or project to see if you might have something off in your current project that’s causing it if nothing else seems to work might help you narrow down the cause.