Hello,
Second line indicates that Source IP 10.0.100.2 port 49184 is NATed to Y.Y.90.159 port 21771.
Since it is a policy based VPN, I assume that you do not intend to NAT the traffic & due to some configuration, it is getting NATed.
Can you show the Source NAT configuration present in your configuration?
Regards,
Rushi