The confusion is probably that you are trying to “skip” game phases unecessarily, or confusing the order of the game phases. Game phases arent skipped for everyone, only the nation that just lost its capital, and the skipping is just because of the way the purchase phase requires money in order for you to buy. The situation you outlined should not be possible according to the normal game mechanics. When a capital is taken, the defeated players money is given immediately to the nation that conquered the territory. Even if Germanys capital is liberated “immediately” by Japan, Germany will still have 0 ipcs to spend at the start of their turn. You must control a capital to collect income, but this doesn’t restore the income you just lost. So for the purposes of “skipping” phases, what is really happening is no money=no purchase=no placement (for Germany). If you liberate Berlin and manage to collect income the following round, there still shouldn’t be units dropping from Germany the round after the capital is taken. The order of game phases is fixed, if G retakes Berlin on combat then they collect income again. If they do not control Berlin at the start of their turn they wouldn’t have been able to purchase units. If Germany is purchasing units it means they have money from the previous round and control of a capital at the begining of their turn. If either of those conditions isn’t met then G has no purchase to make.
Game phases are always the same.
Each nation has its own turn in the game round and this continues in the same order by nation, even if capitals have fallen. Purchase, Combat, Non Com, Placement, Collect Income (provided you control a capital) then on to the next nation and repeat.
Hope that clarifies things a bit