I think I have noticed that also but I think my problems are more complicated. In the meantime I have tried substituting LP-5 for Loopy to see if that clears things up. Interestingly, SLM also indicates it's getting clock from an external source from that app as well and, like Loopy, you have to establish that connection manually. In any case, when sending clock from SLM, if I observe the tempo in LP-5 it varies up and down by as much as 5-10 BPM and behaves erratically. In contrast if I send clock from Loopy to LP-5 it behaves much better. That is the tempo stays fixed and locks consistently. Perhaps there is something affecting the clock output from SLM?
I figure this kind of thing is maddening to track down so kudos to you for being willing to participate in this dialog.