For some reason cw refused to continue after
exten => fax,n,NoOp(RX: PHASEESTATUS is ${PHASEESTATUS})
with generating the pdf.
Could you help me please?

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exten => fax,1,SipT38SwitchOver()
exten => fax,n,NoOp(Incoming Fax)
exten => fax,n,System(mkdir -p /var/tmp/fax/${FAXEXTEN})
exten => fax,n,Set(LOCALSTATIONID=Faxserver)
exten => fax,n,Set(LOCALHEADERINFO=Fax ${FAXEXTEN})
exten => fax,n,Set(FAXFILE=/var/tmp/fax/${FAXEXTEN}/${UNIQUEID}.tif)
exten => fax,n,Set(FAXFILENOEXT=/var/tmp/fax/${FAXEXTEN}/${UNIQUEID})
exten => fax,n,RxFAX(${FAXFILE},ecm)
exten => fax,n,NoOp(RX: REMOTESTATIONID is ${REMOTESTATIONID})
exten => fax,n,NoOp(RX: PHASEESTATUS is ${PHASEESTATUS})
exten => fax,n,GotoIf(${PHASEESTATUS}!=0 ? end : tiff2pdf)
exten => fax,100(tiff2pdf),NoOp(TIFF wird in ein PDF verwandelt.)
exten => fax,101,System(tiff2pdf /var/tmp/fax/${FAXEXTEN}/${UNIQUEID}.tif > /var/tmp/fax/${FAXEXTEN}/
${UNIQUEID}.pdf)
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snip

Here's the relevant part from the full-log:

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Jun 14 11:24:28 VERBOSE[3054316464] logger.c:     -- Executing NoOp("SIP/1xnet-1.sip.mgc.voip.telefonica.de-XXXXXXX", "RX: REMOTESTATIONID is XXXXXXX")
Jun 14 11:24:28 VERBOSE[3054316464] logger.c:     -- Executing NoOp("SIP/1xnet-1.sip.mgc.voip.telefonica.de-XXXXXXX", "RX: PHASEESTATUS is 0")
Jun 14 11:24:28 VERBOSE[3054316464] logger.c:     -- Executing GotoIf("SIP/1xnet-1.sip.mgc.voip.telefonica.de-XXXXXXX", "0!=0 ? end : tiff2pdf")
Jun 14 11:24:28 VERBOSE[3054316464] logger.c:   == Auto fallthrough, channel 'SIP/1xnet-1.sip.mgc.voip.telefonica.de-XXXXXXXX' status is 'UNKNOWN'
Jun 14 11:24:28 DEBUG[3054316464] cdr_sqlite3.c: CDR SQLITE3 SQL [INSERT INTO cdr (clid,src,dst,dcontext,channel,dstchannel,lastapp,lastdata, start,answer,end,duration,billsec,disposition,amaflags, accountcode) VALUES ('"+49XXXXXXXXXXX" <+49XXXXXXXX>', '+49XXXXXXXX', '49XXXXXXXX', 'default', 'SIP/1xnet-1.sip.mgc.voip.telefonica.de-XXXXXXX', '', 'GotoIf', '0!=0 ? end : tiff2pdf', '2007-06-14 11:23:43', '2007-06-14 11:23:43', '2007-06-14 11:24:28', 45, 45, 4, 3, '')]
--------
snip