I can monitor similar effects, especially on the edge of reception range.
In each ADS-B is a section for error detection, but it's possible that this detection mechanism is true, although decoding errors have occurred while receiving the message. This happens, if the message(s) are scrambled in a way that the plausibility check is still true, so the message is marked "valid" and is processed. It's a known issue of plausibility checks and error detections, that aren't using very complex algorithms.
Weak signals on the edge of reception range and/or broken, damaged transponders increase the possibility of such decoding errors, resulting in "airframe jumps".
Further there might be a bug, a glitch or bad programming in the software, which is responsible for this kind of in-precise handling in cases of "edge receiving".
