GM on 10m WSPR: back-scatter?

In the last 2 weeks my 2W WSPR signal has been spotted no less than 55 times by GM4WJA (624km) in IO87mn which is midway up Scotland, not too far from Elgin. Skip this short is not uncommon on 20m but rare on 10m in my experience. This seems too close for Es so maybe it is F layer back-scatter? It is also a bit early in the spring  for Es.  It is too regular too. It seems too far for tropo too or aircraft scatter.