There clearly is room for improvement in our MIDI clock performance. But, note that the test you are using is not very meaningful – since both boxes you show only display BPM in whole values, with no decimal point, it is quite likely that they could show value a BPM apart. For example if the sender is sending 120.6 it might display this as 121, whereas the receiver might display it as 120. This would also explain why it is different when moving in different directions.

Our own silly fault for displaying the received value – you will note that almost nobody else does. Not saying we don't need to improve it (it's on the list), just that this is not a very meaningful test. The only thing that matters here is how it sounds …