"Normal" support structures bulging out

I’ve printed a few parts now with normal supports, and all of the supports bend and bulge out during the print, seemingly under their own weight. Here are two images of the support structure after being separated from the object:


If you look closely, you can see that every single vertical support is bulging out, not just the outermost one.

The bulging out creates downward sag in the support height, which leads to incorrect separation distance with the overhang/bridge first layer, which leads to those layers separating from the top of the supports and warping significantly.

I’m using an X1C with latest version of BS, with hatchbox abs. I’m using all of the default print settings (0.28 extra draft profile), and using the BS default settings for hatchbox abs filament. My chamber temp sits at around 42C during the print.

Anybody know what the issue is and how I can correct this?