Table tops always fail

Fellow woodworkers,

I need your word of expertise: I am heavily into woodworking for the past 2 and a half years, working with solid wood (not weneer or MDF), building furniture and cutting boards with mostly oak, walnut, cherry.

At this point I have enough customers and business to quit my office job and pursue woodworking full time, but I keep having the same problems over and over again: my table tops always fail.

Smaller or larger cracks always appear in the wood table top.

I mostly use white oak, always dry (9-12% humidity), always cut out the center (heart)out, always alternate the grain direction (upward-downward).

Finish either with PU or Rubio Monocoat, but the result is always eventualy the same - cracks appear.

I see some comments about attaching the table top to the base - every table I've done has threaded inserts. The screw hole is always about 4 mm wider than the screw body. Latley, I use oval holes in the metal bases.

Please tell me what am I doing wrong? Is that normal for solid wood table tops? How do you explain it to the customers?