I know this is addressed to Spectr but it would kinda neat if we all posted our experiences with lockups so here's mine.
I've built 4 cams with no timers and 5 with timers. Using mostly the 4 cams with no timers I've never had any of my cams "lock up". I know it can happen but I think if you put the cam on a trail or place where deer enter and leave a feeding area you "probably" won't have any problems.
If I build anymore I doubt I'll use a timer. It a great design and these guys did a great job with it but in my settings for the cam I just don't think I need it.
For all the peeps just getting started I would suggest building one without the timer first. You can always add it later.