enabling multicast on L3 switch kills my wireless traffic

[support@jys.org]

homelab with a single C3560CX-12PC-S L3 switch and multiple VLANs (6), no ACLs (yet).  Wireless being provided via 2 AIR-AP1852I-B-K9 aironet 1850i.  intervlan routing working just how I'd like it to until I turn on multicast routing on the L3 switch.

As SOON as I enable multicast routing on the switch and send traffic across the wireless from one vlan to another - the wireless dies - the ad hoc Mobility Express controller and the 2 WAPs can then only be reached from the native vlan (wired).  No traffic is passed from wireless devices to any other vlan.

Devices directly connected to the switch still route from one vlan to another to the other wired devices as if nothing happens.

software versions:

C3560CX-12PC-c3560cx-universalk9-mz.152-7.E3

AIR-AP1852I-B-K9 - v8.10.142.0

I've setup syslog and watched the transition occur, and there's nothing interesting in the logs.  The switch's routing table doesn't change.  cdp looks good, vtp - good, nothing pruned.   It's like...the trunk ports that the WAPs connect to stop trunking/passing tagged traffic? - because of multicast?  doesn't make sense to me.  I'm completely stumped. 

The only way to get everything back is to reboot the entire network - disabling multicast/rebooting the wireless controller (ME) doesn't do it.

As an experiment/workaround, i installed a junky old c2960 10/100 with a couple of power injectors to get the waps online.  trunked and everything, tested the inter vlan routing - good, then enabled multicast-> all good!  so, there's something between the 3560 and the aironets that goes off in the weeds when I turn multicast on.  I haven't the foggiest idea what it is though.

wasn't sure if this is a routing, network, or switching question

[paul driver]

Hello

Have you tried blocking multicast on the WAPs uplinks

int x/x

switchport multicast block

[support@jys.org]

no I haven't done that - the goal is to have multicast enabled for wireless endpoints (iOT devices, sonos, etc). 

I've done more experimentation, and can verify that something weird is happening on the trunk that the WAP is connected to - either the L3 stops routing traffic on that trunk port, or it's getting filtered, or something else.  I need more data before I can narrow it down.

I put another switch (call it SW2) between the WAP and the L3 - no vlan traffic on that trunk gets anywhere (used a laptop on various vlans), but inter-vlan traffic does get routed around other trunk ports on the L3 - it's definitely that port that is behaving oddly.

VTP shows nothing (pruning is explicity disabled), routing table is good, stp shows nothing. Compared that trunk to all the others on the same L3, and it's the same for everything I know to look for.

I can connect from the L3 to SW2 so i know it's not 'dead', but not from anywhere else, not even from the management vlan on a different port on the L3 - which is....odd....

I see nothing special - anyone have any ideas?  This is starting to get over my head.