YES, I thought it was just me having a difficult time.  I have had more errors with cartridges with Code 22 mixing errors too.

The sample well on the ACT cartridge is shaped a little differently than some of the other i-Stat cartridges and I think it somehow gets a trapped air bubble that blocks the sample.  We instruct staff to use a blunt needle and insert it slightly into the well to avoid this issue.  We also tell them to always have at least one more cartridge than they need at room temp so they don't have to redraw if they run into this issue.

I have tried a blunt needle and still have had an issue, not with every cartridge but with a few

No idea if this is "abbott approved"... but I've had good luck GENTLY tapping the cartridge flat on the counter. I don't know if it's due to surface tension or what, but it does seem to help. 

Have any of you reported the issue to Abbott? We have a case open with Abbott regarding Subtherapeutic ACT values after standard heparin dosing, the issue has been reported from multiple hospitals throughout the United States with many sites reporting cartridge fill issues.

I have also reported the subtherapeutic ACT values and reported the cartridge fill issue today.