VLAN Routing Problem

I have a simple network set up with a GSM7328S (V2, I think) and a GS724T. I have a 4 line lag between them and a few vlans that appear in both switches. The lag between the switches has all vlans tagged between them. I have the lag in PVID 1, set to VLAN Only.

Both switches serve as core and edge - some ports have PC's connected and have PVIDs of the VLAN the PC uses, Admit All, with the port set to untag for the VLAN used (something other than 1). The GSM has several sets of 2 LAGS going to Hyper-V hosts; one for the host, which is config'd like a ports described above, and the other has all vlans tagged to the LAG with PVID set to vlan 1 (default) and VLAN Only. I have VLAN Routing set up for all VLANs, config'd via Web with x.y.z.1 as the address for the router interface. Inside the Hyper-V server, VMs are configed to use the necessary VLAN at the virtual NIC.

All VLANs used by server are on a VLAN other than VLAN 1. The two switches and one workstation used to configure the switches are the only devices on VLAN 1.

All VMs, PCs and network devices communicate within their VLAN and across all VLANs, so all routing is working and all is well - except for one thing.

No device, physical or virtual, can ping any of the IP addresses that the GSM has as a VLAN route interface address. Pings fail from any device to it's default gateway and to any of the other VLAN's default gateway. The GSM can't be managed from any of the VLANs (this is good), but some devices need to be able to ping their default gateway to work properly (don't as me why, but it's a requirement for some of my devices, plus, one should be able to ping one's default gateway).

There is one acception to this - the one PC that is on VLAN 1, that is used to manage the network switches - it's able to ping all default gateway addresses for all subnets and VLANs, plus manage the switches.

So my question is, why is a PC that's on a VLAN, untagged, set to Admit All, with a PVID set to the VLAN unable to ping the VLAN router port that is obviously routing properly?

Some additional info:
On occasion, the device will return a ping from the default gateway address. Sometimes days pass before this occurs and it never works for more than a few minutes at a time. Yesterday, suspecting that I have something misconfigured, I did a factory reset on both switches and rebuilt the configuration - and got the same result. I've been dealing with this for some time and need to know what I'm missing. Docs related to setting up routed VLANs don't ever deal with the L2 switch (GS724T) carrying the VLANs, but tend to set up port routing to IDFs.

Any help would be appreciated. It seems simple enough that devices on routed VLANs in a GSM device should be able to ping the VLAN router address.

I can provide more config info if anyone is interested.

Jim Graczyk