Quoted from Nevus:https://pinside.com/pinball/forum/topic/ultrasonic-cleaners/page/10#post-3132303
Update on above post from 8 months ago.
My 6L Chinese unit from eBay is going strong. No problems and it cleans well.
Did you find a time/temp/cleaner that works best for you? I just purchased the same 6L unit.