I reported that it was now totally failing, stuck on processing forever, and was told
"Thanks for the reports, and sorry for the wasted attempts. The kohya training engine has been unreliable and is being retired, so we are not putting further fixes into it. Training on the ai-toolkit engine is stable and is the recommended path going forward. Every failed kohya run auto-refunds, so you were not charged for those attempts."
This isn't good: For Illustrious AI Toolkit has proven terrible at characters, and bad at concepts.