I've had the Perrin 19mm sway bar before but didn't run into this issue. @
strat61caster is right the first step is to contact customer support and hopefully get them to send you replacement bushings. You absolutely do want the bar to freely articulate up and down. I personally wouldn't run bar bracket spacers...I think you'll find a way to free up the bar without them.
I don't think it would be a problem installing 20mm bushings if that didn't work out.
Also, when you applied ze lube did you lube just the inner portion of the bushing, or did you also do it on the bar itself where the bushing sits? I like to include the bar as a place to lube since grease may be squeezed out of the bushing when slipping it on, especially when the hole is small diameter relative to the whole bushing.