UDP truncation

[Vladimir Kudrya]

Hello everyone!
Could you help me with UDP truncation problem?
I have three hosts, two on broadband connection, one on 4G (lower MTU).
Judging by tincd logs, MTU discovery works, for example on 4G host:

     tincd[4598]: Got MTU probe length 1363

TCP inside the VPN network works fine, but UDP is truncated. By testing 
with iperf and dumping traffic I get this:

Between broadband hosts:
     20:45:04.259936 IP (tos 0x0, ttl 64, id 52068, offset 0, flags [+], 
proto UDP (17), length 1444)
         10.2.0.1.5001 > 10.2.0.3.54616: UDP, bad length 1470 > 1416

Between broadband and 4G hosts:
     20:48:11.769469 IP (tos 0x0, ttl 64, id 21621, offset 0, flags [+], 
proto UDP (17), length 1348)
         10.2.0.2.46650 > 10.2.0.1.5001: UDP, bad length 1470 > 1320

ICMP is allowed both inside and outside of tunnels. All hosts are Debian 
testing with tinc 1.0.28.