Did you manage to resolve your problem? I have a problem quite similar to yours with my solid wood oak flooring. The floor overall -between the opposite house walls- has a ripple effect, looking like the sine function. The installer used a floating installation method over a concrete subfloor, with a one-sided self-adhesive underlay that holds the flooring planks together. The floor was installed 6 months ago and started to look like yours in the photo (but not to that extent - yet). I suspect (and hope that) it must be due to summer expansion and inadequate expansion gaps, particularly at points where it touches on the door and window frames. It would help if you let me know if and how you resolved your issue. Thanks!
