Synchronisation ? How ?

Small summary of the facts :

Yesterday evening by going back home, having played on my IPhone, I had on the game 3.089.000 coins.
Then I passed on the IPad (for the 1st time for a long time) and the game synchronized with no problem at all, I was able to continue to play with my balance exact.
Before sleeping me yesterday, I had reached 3.371.000 coins, that is almost 300.000 in more.

This morning, that must leave, I launch the game on my IPhone, but no synchronization. I find my balance of 3.089.000 coins.
I close the game and I wait to return to see on the IPad.
After launch of the game on the IPad, it synchronizes again, making me pass 3.371.000 in 3.089.000 coins…

I thus lost 300.000 coins, gemstones, hours of game, the progress in the successes of the game…
Can anybody explain to me how works this synchronization ? Because as for Epic it is in 2 directions, as here, passed of the IPad in the IPhone seems to me impossible.

And on IPhone as on IPad, I have the same account FB and the same account GC.

Thanks