Large SCP transfers blocked

I am finding that large file transfers (about 1.9GB in this case) via scp (secure copy using ssh) fail between my system and multiple servers at various sites from my Comcast internet.   When I take the laptop to my other home where I have Verizon FIOS, scp of this size file works first time, every time (I tested to several different remote servers at different locations).

Is there a problem with Comast reliability or is the system intentionally injecting bad packets or dropping data to prevent this sort of use of consumer internet?