Hello friends! Greetings.
It seems to me that if your car is driving white smoke, you should verify several things:
Do you consume motor oil? Consume water/refrigerant? Is the engine overheat? How many km does that engine have? It is also advisable to perform a compression test to rule out that it is oil pass through the rings.
If your engine consumes oil, and presents the symptoms that you describe, it is likely to be cold oil consumption by worn cylinder rings, when heated, the rings dilate increasing their size and thus improve compression and decrease the oil passage to the combustion camera. Check the spark plugs, they may be full of oil.
It may also be that the camera (cover or cylinder head) presents deformations in the union plane to the block that can be caused by motor overheating.
However, it seems very rare for mechanics to review your car and have not found the cause of this abnormality.
I hope I have helped