We had Preverco Engenius Walnut Select installed in the first week in January. As of Feb 1, there were 50 instances of boards splitting (the same 2 cracks) from one end of the board all over our first floor.

Does anyone have any ideas what could cause this and what our long term issues will be with this? The installer is saying it is a result of temperature fluctuation in the house. However we have the same floor installed upstairs in the games room and it has maybe 2 instances of this (vs the 50 instances on the first floor).

Help.

Seldom will the humidity be the same from upstairs to the bottom floors.

My guess is the downstairs is much lower in rH, then the upstairs.

Wood shrinks to a point, then it cracks. The key is, to not let the humidity get so low, it cracks. Winter time is heating season. Heat dries wood out.

In the wood flooring world, Thanksgiving is the start of gap and crack season.

Ya, sounds humidity related, although I believe; the humidity will be lower on the upper level, so not sure how that applies. Although, if it is an active household with lots of people showering daily that could have an impact. Increasing your humidity during heating season, and damp mopping the floor occasionally will help. But! damp mop does not translate to using a bucket of water and a deck mop.
Best way to control the interior environment is with a properly installed and maintained humidifier on the furnace. Idealy, if you can maintain 45% RH year-round, Floor will sit there and look pretty. This is a daunting task, so 35 to 50 is acceptable to most manufacturers.