Need help with basic layer 3 switch configuration

Hi everyone, I could use some assistance doing what should be a pretty basic layer 3 switch configuration.

I've got a site with three existing VLANs and subnets. Currently the physical router device is routing inter-VLAN traffic. They are as follows:

VLAN 1 (default): 192.168.31.0/24
Gateway: 192.168.31.1

VLAN 2 (mgmt.): 192.168.131.0/24
Gateway: 192.168.131.1

VLAN 3 (guest): 192.168.231.0/24
Gateway: 192.168.231.1

Another group will be joining the existing network, that group will have their own subnet 192.168.103.0/24 which I will be placing on VLAN 4 at the main site. I have a layer 3 switch (Netgear GSM7328FS) that I will be using to route VLAN 4 to VLAN 1 as I should get better performance routing with this device than the physical router. This group will also be sharing VLANs 2 and 3. Switch port connecting to this office will be configured as a trunk (Cisco language), so it will be an untagged member of VLAN 4 and tagged member of VLANs 2 and 3.

The switch management interface is 192.168.31.25 on VLAN 2.

I've assigned IP addresses to the VLAN interfaces as follows:
VLAN1: 192.168.31.254
VLAN4: 192.168.103.1

Routing is enabled on the device and the interfaces. I've got a route statement in my physical router for 192.168.103.0 next hop 192.168.31.254.

Now for the question, why I'm not able to reach 192.168.103.1 (VLAN 4) from the other side?

If I attempt to ping from 192.168.31.0 I get:
Reply from 192.168.31.254: TTL expired in transit.
Reply from 192.168.131.1: TTL expired in transit.
Reply from 192.168.131.1: TTL expired in transit.
Reply from 192.168.131.1: TTL expired in transit.

If I attempt tracert, I get:
Tracing route to 192.168.103.1 over a maximum of 30 hops

  1     <1 ms    <1 ms    <1 ms  192.168.31.254
  2       1 ms     1 ms      <1 ms  192.168.131.1
  3   145 ms     2 ms        2 ms  192.168.31.254
  4       1 ms     1 ms        2 ms  192.168.131.1
  5       2 ms     2 ms        2 ms  192.168.31.254
  6       2 ms     2 ms        2 ms  ...

I have no idea why the x.x.131.0 subnet is even involved. Hopefully this behaviour will throw up a flag for someone, and you can point me in the right direction. Thanks in advance


*** Edit ***
After sitting for a while, now the pings just time out, as does tracert. I've also thrown up a quick screen shot of the routes as configured in the device. I feel like the problem lies in something that's there (or not there).