Snow mines missing some snow blocks

[Knarfi]

What is the bug: Upon reset the mine is not always fully filled with snow and ores. It seems that random snow blocks around the redstone lamps are broken/getting melted. As visible in the screenshots there is random snow (as item) laying around which indicates it was broken, to me this indicates that the snow does spawn but breaks instantly. It also seems that ore blocks are not affected, as seen on the screenshot they do not seem to be broken/removed.
I experienced this bug multiple mine resets, but NOT ALWAYS, since yesterday.

Where is this bug located: Snow mine at E.

How can we recreate it: Wait for the reset of the snow mine.

Screenshots:
http://imgur.com/a/mZXVx  (imgur album)

Greetings,
Knarfi