The last time I noticed this (it has happened more than once) I sent 1 the first time and got a partial report and 9 the second and got a full report. I know that in the past I had to send at least 6 in the same situation.

If you send 2 probes you will get a full report on anyone with less esp level than you and you will get everything but research for someone with even level, and everything but buildings/research for those with 2 above you. Beyond that, I've worked out whats up but I'm not sharing .