Bad UDP Length > IP Payload Length
There are a number of potential problems with this.  First, even though your application may be configured for an assumed MTU, it's not possible to tell from your description whether that actually affects the bytes on the wire.  For example, under Linux, the MTU may be limited to 1500 (or some other number) by the driver or by the hardware.  

Second, with IPv4, any intermediate device can fragment a packet and send two (or more) pieces if the size exceeds a link's MTU.  That's probably not the issue here, since both devices appear to be on the same subnet with non-routable addresses, but it could limit your options in the future.

What you're looking for is support for Jumbo Frames, so check that the chipset and driver on the other end handles them.