Just noticed a not-so-weird situation!
I'm animating a rect-box and have a STM component set to fit the box with some padding. As the animation set the box to be smaller than the padding I end up with a negative rect-transform width which causes STM to render the text by default!
I could make a script that just forces the rect to not be negative or disable the STM component when the width is smaller than 0, thought I'd just post this in-case there is already a "fix" or similar solution :-)
STM saved our project btw <3