Problems with 2 WANs and simple routing

Hello everyone!

I have a RB3011UiAS running RouterOS 6.38.1
it is connected to outside through 2 providers WANs (1 on SFP, and other on ether1).
I have 2 LANs (main:ether2 [with ether3,4,5 bridged] and ether6 as separate for testing).

set [ find default-name=sfp1 ] advertise=10M-half,10M-full,100M-half,100M-full comment="WAN VOLTA" name=SFP
set [ find default-name=ether1 ] comment="WAN Net-Pol"
set [ find default-name=ether2 ] name=ether2-master
set [ find default-name=ether3 ] advertise=10M-half,10M-full,100M-half,100M-full master-port=ether2-master
set [ find default-name=ether4 ] master-port=ether2-master
set [ find default-name=ether5 ] master-port=ether2-master
set [ find default-name=ether6 ] comment="test port"
set [ find default-name=ether7 ] master-port=ether6
set [ find default-name=ether8 ] master-port=ether6
set [ find default-name=ether9 ] master-port=ether6
set [ find default-name=ether10 ] master-port=ether6

I want to force traffic from ether6 through SFP only, I have set up mangle rules to mark routing from ether6 and SFP as below:

add action=accept chain=prerouting dst-address=193.26.131.42 in-interface=ether6
add action=mark-routing chain=prerouting in-interface=ether6 new-routing-mark=do_Volta passthrough=yes
add action=mark-routing chain=prerouting in-interface=SFP new-routing-mark=do_Volta passthrough=yes

also i have setup the routes for this mark:

add check-gateway=ping distance=1 gateway=193.26.131.41%SFP pref-src=193.26.131.42 routing-mark=do_Volta
add distance=1 dst-address=10.10.10.0/24 gateway=ether6 pref-src=10.10.10.1 routing-mark=do_Volta scope=10

This seems to work, however some pages (msn.com, bing.com, and others) won’t load. Looks like some packets are not returning.
My question is: Is there an error in my configuration, how to correct it ? Any advice appreciated

Try also adding;

/ip firewall mangle
add action=mark-routing chain=prerouting in-interface=ether6 new-connection-mark=do_Volta passthrough=yes
add action=mark-routing chain=prerouting in-interface=SFP new-connection-mark=do_Volta passthrough=yes

I use a similar setup for an application I do and I have both new-connection and new-routing marks and it works fine.