Dual WAN SSL performance issue

Hi

I have dual-WAN set up, with most of devices being routed via first ISP, and some devices being routed via second ISP.
But after update to 6.38/6.39 i have strange performance issues when accessing SSL sites via second ISP: everything became dramatically slow. Any SSL-enabled site opens very slowly.
But, if i open Torch on second ISP interface - sites access speed gets to expected levels.

Any ideas, what could explain this behaviour, and how it could be fixed?

P.S. Dual-WAN access is set up using mangle & src policy routing.