Unable communicate with NAS after its VPN connection is established

I'm sure there's an easy solution for this issue but I'm largely inexperience so am struggling. Topology is as follows:

I have 3 local networks:

Default: 192.168.0.0/24 IoT: 192.168.107.0/24 Guest: 192.168.10.0/24 

I run the Proxmox hypervisor from the default network. Its IP is 192.168.0.100 . Proxmox hosts 3 VMs of which 2 are located on the IoT network (VM1: 192.168.107.50 and VM2: 192.168.107.15 ). My Synology NAS resides on the default network and its IP address is 192.168.0.152 . This is a bonded connection by ethernet ports 1 & 4.

My issue is that when the NAS is connected to the VPN (switchVPN) although it is reachable from the default network, it is unreachable from the IoT network. Pinging to or from the NAS into the IoT network is unsuccessful.

When the NAS is connected to the VPN:

IP: 10.60.0.195 Broadcast: 10.60.0.255 Gateway: 10.60.0.1 

Connecting an additional ethernet cable from the NAS, separate of the Bond connection creates a new IP address for that connection 192.168.0.154 . This behaves the same way as the bonded connection.

Not sure if its relevant or not but hardware wise the Unifi USG feeds into a 24 port Unifi managed switch.

Any help would be hugely appreciated. I've been battling with this for some time now. TIA.