This log will not help to analyze the issue. It is system log catched by device itself - it carry no information related to voice operations. Turn on syslog&debug messages (highest level) on voice tab and send them to an external syslog server.. It;s different log that the one you attached.
Also, catch the SIP packets.
Fax session is failing either because you are using compressed codec. Or because there is T.38 misconfiguration. Or because fax is selected so high transmission speed. Or because end-to-end IP connectivity is poor.
Captured SIP session will disclose codec used as well as T.38 thinks. You should configure your fax not to use speeds over 9600Bd and it should not use V.34 modulation as well.