wtperf update-lsm failure

The most recent run of wtperf with the update-lsm.wtperf config failed with:

[wiredtiger-perf-update-lsm] $ /bin/sh -xe /tmp/hudson4165151652224983747.sh
+ cd build_posix/bench/wtperf
+ rm -rf ./WT_TEST
+ mkdir ./WT_TEST
+ ./wtperf -O ../../../bench/wtperf/runners/update-lsm.wtperf
read not found for: 00000000000004048252. Value was inserted during populate Error: WT_PANIC: WiredTiger library panic
Build step 'Execute shell' marked build as failure

It might be another manifestation of WT-664. I am trying to reproduce it and then see if the lsm-checkpoint-lock branch fixes it. So far it is not reproducing and is running well.