I don't think I have completely lost my mind yet, but I do think that Notion is confused about rhythm. In the attached image, I have a full measure of 16th note triplets.
Notion seems to think that there are 4.5 beats in the measure. I have tried entering it as a custom tuplet putting 6 into 4 but it produces the same result. Have I done something wrong in the input? The following measure--the one with just a whole note--simply cuts to silence around the "and" of three in the running 16th note triplets.