Prohibited transactions - excise tax Form 5330

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Facts: In 2010, forfeitures from Plan A were used to offset employer contributions to Plan B. In 2011, Plan Sponsor realized this was not allowed and repaid the funds back to Plan A but in the process some funds from Plan C were used to repay the funds from Plan A to Plan B. In 2015, the funds were returned to Plan C.

I think there are two prohibited transactions: (1) forfeitures from Plan A to Plan B used as employer contributions and (2) funds from Plan C used to repay the forfeiture from Plan A to Plan B.

Both transactions are considerate continuous transactions and need to file Forms 5330. Is this correct?