CD34 in thawed PBPC

In our BMT cell processing Lab, we routinely detect CD34  on PBPC after
collection(fresh PBPC) and before infusion(thawed PBPC).  We often find CD34
express in Thawed PBPC was higher than in fresh PBPC(same product). We use
ISHAGE method to calculate the CD34. We also use 7AAD to exclude the dead cells.
In the dot-plot(CD34PE vs SSC), we sometimes see denser or bigger population in
thawed PBPC(compare to fresh same PBPC). Anyone has same experience? what are
possible reasons to cause this? Is  there any way to solve this problem and  get
more accurate % CD34 and recovery?  Thank you for your precious opinion.

Jay