Bit stumped by that one, I used your values and the same build and timeshift works fine.
You already said that it works if only RAM is enabled as my next question would have been which streaming profile are you using as I'm fairly certain timeshift only works with the HTSP protocol.
Does /var/log/syslog throw up anything useful and have you tried enabling debug and/or trace options to see what errors (if any) tvheadend is spitting out?
