[asterisk-r2] Looks like Oi/Brasil Telecom is not signalling collect calls anymore?

[Norman Schmidt]

During months, the collect call blocking capabilities of OpenR2 were working
like a charm, using it with Asterisk 1.4.21.2, Zaptel 1.4.12.1 and OpenR2
1.1.0. 

Suddenly, some days ago all E1 R2 trunks we have with Oi (ex-Brasil Telecom
here) started to accept collect calls. These calls are passing thru not
signalled as collect calls anymore:

[Aug  7 11:53:10] NOTICE[9103]: chan_zap.c:961 zt_r2_on_call_init: New
MFC/R2 call detected on chan 1.
[Aug  7 11:53:12] NOTICE[9103]: chan_zap.c:1025 zt_r2_on_call_offered:
MFC/R2 call offered on chan 1. ANI = 51XXXX0017, DNIS = 0200, Category =
National Subscriber
[Aug  7 11:53:13] NOTICE[9103]: chan_zap.c:1093 zt_r2_on_call_accepted:
MFC/R2 call has been accepted on chan 1
[Aug  7 11:53:13]     -- Executing [0200 at ENTRADA_PRINCIPAL:1]
NoOp("Zap/1-1", "TIPO DA LIGACAO - National Subscriber") in new stack

As far as I remember, "Category" was being signalled as "collect call" or
something like that for collect calls before (and blocked by
mfcr2_allow_collect_calls=no accordingly), but now all calls come in as
"National subscriber", even the collect call ones. 

I tried "mfcr2_double_answer=yes", but then:

[Aug  7 11:54:52] NOTICE[9472]: chan_zap.c:961 zt_r2_on_call_init: New
MFC/R2 call detected on chan 1.
[Aug  7 11:54:57] WARNING[9472]: chan_zap.c:1199 zt_r2_write_log: Chan 1 -
MF back cycle timed out!
[Aug  7 11:54:57] ERROR[9472]: chan_zap.c:1202 zt_r2_write_log: Chan 1 -
Protocol error. Reason = Multi Frequency Cycle Timeout, R2 State = Seize ACK
Transmitd, MF state = Category Request Transmitted, MF Group = Backward
Group A, CAS = 0x00
DNIS = 0, ANI = , MF = 0x30
[Aug  7 11:54:57] ERROR[9472]: chan_zap.c:1012 zt_r2_on_protocol_error:
MFC/R2 protocol error on chan 1: Multi Frequency Cycle Timeout
[Aug  7 11:55:02] NOTICE[9472]: chan_zap.c:1225 zt_r2_on_line_idle: Far end
unblocked on chan 1

Can I start to blame/curse Oi/Brasil Telecom only, or do I have any
alternatives? Do someone else here on (south of) Brazil facing similar
problems with ex-Brasil Telecom E1 trunks (now "Oi")?

Norman