Well, after doing a lot of tests, I think that @wolfgangschaltung and @sezare56 were right when they said a few posts back that you had to start from the silence, at least to make continuous environmental sounds / drones.
My conclusion is that recording buffers do not like to have any signals when they start recording. If so, make noises, clicks, pops, hiccups, … and the Overdub Do not take it away!
But if you start to record in silence and then you go up the volume of your recorder buffer source and overdub while you go down, you get a seamless loop, continuous, that overlaps well.
if you cut it when finished it also happens, there will also be clicks.
100% of the tests have gone well doing so. In my case the configuration has been:
-Track1 with Pickup, inputs -, SRC3 = CUE, fades = 0, Qrec and Qplay = Off, Len = Max. Pickup without FX, Attack = 0.
-Track2 with Thru machine, input (where you have your instrument), Cue activated.
-Settings of memory, without reserved memory and dynamic assignment ON.
-Select the track1, open the Mixer, press Rec AB, then in the mixer raise the CUE from -64 to the desired volume. Press Rec AB (with One2) to enter Overdub and start decreasing the Cue in the mixer until you reach -64. Press Rec CD. The loop will not have noises.
Regards,