settingsのoptimizationsの
> Pad prompt/negative prompt
>(improves performance when prompt and negative prompt have different lengths; changes seeds)
> Pad prompt/negative prompt (v0)
>(alternative implementation for the above; used prior to 1.6.0 for DDIM sampler; overrides the above if set; WARNING: truncates negative prompt if it's too long; changes seeds)
のどっちかのチェックかな？
そういう時はsettingsのsearch欄に「pad」って入れてみるよし