[mlag]

Once had it, on my camera with older battery going low (1 bar out of five, usually it shows first 0 bars before camera stops working). Other smaller screwdrive lenses still worked fine on the camera , only the 150-450 started to focus again with other full battery...
So my current (working) assumption is that this lens draws more current than average and my older battery was not up to the task. Might be hsm focus related, maybe more sensitive to weak battery than screw drive lenses I could test at that occasion...
One occurrence is not much, hence the low battery theory is an assumption based on the fact that it worked again after battery swap, and other lenses still worked before swap....

[kkoether]

I was shooting a boat race last Saturday. 5200 shoots for the day and I only had a couple of lockups that required powering down. 1.50 FW. Much better than my first weekend at the races.