I just fixed it.
I had to slow down the scan by increasing the Connect timeout to 2000MS. I currently have my delay timeout at 2000 as well, but I’ll be lowering both of those values to find the best one for us, as I’m pretty sure they both don’t need to be at 2000.
As far as I can tell, the firewall is seeing the scan as an attack and it starts to block it after so many sequential address scans. Putting a delay in seems to do the trick, though!