I may have found the issue and a solution (for some). Noticed a duplicate connection from one site displaying the routing issue: It would seem that the Draytek (as the initiator), for some reason,...

@GRL Thanks for that confirmation. I suspected as much as the TP-Link Omada based sites VPNs are as solid as. The only reason I went with the existing Drayteks was the VDSL connection and the lack of...

Using the Omada software controller, I've setup an IpSec / IKEv2 Site to Site VPN. Omada ER7206 is the Responder; A Draytek Vigor router - on VDSL - is the initiator. The VPN connects and works...