Awa notifications get resent constantly

[mtusnio]

It seems that in some cases Awa gets stuck resending the same notification over and over again, spamming this in the log:

 [DEBUG] [lwm2m_client_core.c:1414] Send Notify to coaps://[FD63:FAB9:6CCF:0064:0000:0000:34D1:526F]:51
 [DEBUG] [network_abstraction_contiki.c:135] Cache hit on look up FD63:FAB9:6CCF:0064:0000:0000:34D1:5F
 [DEBUG] [coap_abstraction_erbium.c:540] Coap notify: coaps://[FD63:FAB9:6CCF:0064:0000:0000:34D1:526F1
dtls_prepare_record(): encrypt using TLS_PSK_WITH_AES_128_CCM_8
 [DEBUG] [lwm2m_tree_builder.c:62] Treebuilder length: 4
 [DEBUG] [lwm2m_client_core.c:1414] Send Notify to coaps://[FD63:FAB9:6CCF:0064:0000:0000:34D1:526F]:51
 [DEBUG] [network_abstraction_contiki.c:135] Cache hit on look up FD63:FAB9:6CCF:0064:0000:0000:34D1:5F
 [DEBUG] [coap_abstraction_erbium.c:540] Coap notify: coaps://[FD63:FAB9:6CCF:0064:0000:0000:34D1:526F1
dtls_prepare_record(): encrypt using TLS_PSK_WITH_AES_128_CCM_8

I'll take a look to see what can be causing that.