I logged into a friends island to buff his gold mines and saw a level 5 mine was down to 7 ore. I bought an omniseeds for 50 gems and applied them to his mine which was then down to 2 ore, It made the jingle sound and removed the omniseeds from my inventory but did not increase the the amount of ore in the mine.

I suspect this is caused by the same game defect which causes geologists to not find an ore source if there is not one at onset of his mission even if several become vacant in the interim, because the game searches for the vacancies at onset rather than completion, and the waiting period is just a formality...

In this case I believe the game had already decided that the mine was empty as soon as the new production cycle started, which was going to be sufficient to drain the mine completely, and the glitch lays in that there is still an active mine to eat the omniseeds, just not active enough to actually receive the contents. Because the game has decided it is an exhausted mine.

I certainly hope I get my gems refunded