https://bugs.openldap.org/show_bug.cgi?id=10552
--- Comment #9 from Howard Chu hyc@openldap.org ---
We have never reproduced this issue in-house, but in the wild it's in the top 10 of our crashes.
One more thought - the default on Windows in LMDB 1.0 is to use write-through writes. Which means all writes go directly to the storage device, instead of sitting around in buffers that need to be flushed. The errors you're seeing are indicative of writes that got dropped, never made it to persistent storage. Most likely these are drives that lie about completing synchronous writes. And if you're using better quality drives in-house, that explains why you've never seen the problem yourselves.
This is unlikely to be resolved by any LMDB patch or even Windows patch, it sounds like flaky hardware.