Dante M. Catoni wrote:
Where did the cracking start? Around commode? Something is rotted?
What do you mean by "wavy" - the edges aren't cut straight or they are
buckled/warped?

It started mostly in the center of the room. All the wood seems to be in
very good condition. I don't see any sign of moisture damage. Last week
my 2 year old daughter dumped a pitcher of water from the tub onto the
floor so there is a stain there, but everything is solid certainly no
sign of long term water exposure. If you put a straight edge across the
boards there might be about 1/16" spaces all around.

Thanks
Dante

If there were dips in the boards not filled with mortar, the space could
cause the tile to crack when pressure applied. See any sign of that on
back of tile?