IPSEC VPN, high traffic over VPN slows down network

HI… i have a few older peplink balance 580 HW 1 and 380 HW 1… everything has been working great so until we noticed this. We have configured it to have an IPSEC vpn tunnel to a Cisco ASA remote colocation.

Whenever someone copys a file or deploys something large thru the VPN… we notice high cpu and it causes DNS resolution and network slowness.

Is this because of the older hardware? would it be resolved with a newer HW revision?
we are assuming the encrypting in the VPN thats causing it… is there a way to fine tune the encryption? like maybe chose a different IKE version?

Please open ticket for us to take closer look. It looks like the device was overwhelmed.