I wrote: Later, soon after take off, PowerFLARM indicated a target 200ft below me and quite close.
In response, Rod1 wrote: "That is exactly what my test unit did when it detected my transponder!"
What mine indicated was a Flarm/ADS-B target, not a transponder. Is that what your test unit did?
Since there were still a few gliders about, and it had not happened after my first take off, I presumed it was a real FLARM target but I will keep my eye out for this in future.
One thing I did do to try to avoid this problem was to switch on my transponder (Mode C) very soon after start up of engine and PowerFLARM, rather than leave on Standby till ready to take off. I know that my transponder takes a while to warm up anyway but reckon that the sooner it is detected and ignored by PowerFLARM the better.
So not sure if this is still a problem or not. And if so, hopefully it will be addressed by the next update in March!