i got shitloads of them today i had a set by an opening with no glass and walked off as usual came back and it was on its way, i had to force it flat with a bit of water ......had them last week when it was too cold cause i was getting on it too early ;D.........there bastards! and everyone gets them from time to time, if you do get them try either wet cross troweling or on the third trowel put shitloads of pressure (like youre trying to push through the wall) before cross troweling .........ive not used a lot of it but ive heard board finish is less prone to tiger striping