I'm seeing some simulation failures at corners/temperature due to negative mobility factors. The easiest way to replicate the issue is change the corner of the

rf_pfet_01v8/tests/sky130_fd_pr__rf_pfet_01v8_aF02W0p84L0p15__pfet_vth.spice

to 'ss'. Although this also happens under other conditions - always lower mobility conditions, hot and/or slow corners. Looking at the spice model, in pfet_01v8 bin 44 (which is the device used) the vsat, u0 are negative. I'm not sure if these values were modified or copied straight from the spectre model - maybe an error has crept in? Should I raise this as an issue on some system, open_pdks github repo?