Trixbox 2.6.2.2 crashes on fax detection or doesn't send complete fax

I have a stock install of Trixbox v2.6.2.2 that's *in production* an working fine.  The box has an 8 port Rhino analog adapter with 6 POTs lines connected and around 10 SIP extensions.  It has been in production for about 5 months and works very well, except for fax detection.  I have scoured the Internet trying to find answers to what could be happening but, thus far, have been unsuccessful.  Basically, we have the following:

- Voice calls work flawlessly.
- Fax *detection* works flawlessly
- When we get an inbound fax, the process of converting the fax to PDF and emailing it seems to start, but doesn't complete successfully
- If we remove libtiff, we get a segfault and Asterisk restarts (calls dropped, etc.)
- If we have libtiff installed, we sometimes get a segfault and Asterisk restarts but, sometimes, it sends an empty PDF and sometimes it sends a partial PDF
- I have another Trixbox 2.8.x box that does the fax to email perfectly.  I know that upgrading from 2.6.2.2 to 2.8.x would be a good route to go, but the dialplan is a bugger and I really hope to find some other way.  I don't know of an in-place-upgrade option to go from 2.6.2.2 to 2.8.x.