If you look at the dividend history of IDVY.L, the dividends have been significantly different from quarter to quarter in the past as well. So I suspect that it's passing through the dividends of its underlying 30 companies that may not pay dividends every quarter. Spot checking a few of its holdings, there are indeed companies in the index that only pay dividends every 6 months. So if there are quarters where only a few companies pay dividends, the fund itself may not have as much to distribute.
Also note that dividends are not like interest, in that they do not produce wealth. The value of the fund will drop by roughly the amount of the dividend, so even if the fund pays a smaller dividend, that just means that the fund will not drop as much. Dividends can be valuable for investors that want periodic cash flow even at the expense of a smaller balance afterwards (rather than having to sell shares periodically), but it is something to be aware of.