Frequent compressor cycling when using a ASHP for shower water heating alone

[nike123]

I see 3 pipes are comming at bottom of cylinder and 1 pipe at side of tank. One connection is blanked.
Middle tank have side outputs which are different in position than other two.
I think we should first confirm that tanks are connected as it should be regarding inlets and outlets.
I think that parallel tanks configuration is better one, but it must be balanced.
Since heat pump works with temperature difference of 5K to 8K at maximum, heat exchanger surface of tank which is made for 10K (or more) differential is to small to transfer effectively heat to water in tank and therefore you experience frequent compressor starts and short running time.
In paralel (balanced) setup, same energy is disipated from 3 times bigger surface and you should have better heat transfer to water in tanks and your heat pump temperature diferential should drop to 5K.
Could you take picture clearly of labels on tanks and translate to english what is written there?