Looping over drum loops

[blasphemier 0]

Using the Spider V 240 with FBV3 and I I’m trying to loop some riffs over the drum loops. Every time I do I notice my loop will unsync from the drum loop pretty drastically. Are the drum loops all in time to a click when they were recorded or do they vary ever so slightly in tempo? The only other thing I can figure is that my timing is way off with hitting the looper on the FBV3.

[thorneven 68]

I can tell you that setting the looper so one stops it at the exact right time takes time to master.  The solution for me is to stop the recording, i.e. press the looper button to stop recording, on the 1 of the next measure.  So if you're in 4/4 and recording a loop that is 1 bar, count 1 2 3 4 and press the button to stop recording on the next 1.  But it has to be precise or you'll find that you're 4/4 time sig has become 4/4 +- 1/16 !