@Birk,
First, can you please try updating to the latest build (v1.73.105 at this time) and try again? If it still fails, can you please tell me if this also happens if you turn Brave’s Shields off for the site (lion icon in the address bar)?
Yeah I figured that might be the case. I’ll have one of our webcompat guys take a look at what exactly Shields is blocking when they have some time so this can be avoided down the road.