MP Install firmware fails but APM Planner works

I think I’ve done all my homework - 64 pages of search results throw up around half a dozen identical issues to mine with no consistent solution:

Mission Planner 1.3.10 on Windows 7, USB connection with 1A of current available. Arducopter (no peripherals connected other than USB) Repeatedly fails to complete reading phase - halts at about 80% saying “Communication Error - no connection”. MAVlink will however connect just fine so USB drivers/virtual comm port all operating as expected. I checked the properties for the comm port to make sure it was set to the same baudrate 115200. Comm port number is quite high (22) but it doesn’t hinder the MAVlink connection. The only other thing I can report is that, to begin with, detecting Board Version takes around 20 seconds which seems a bit long and may hint at something.

Oh, and I almost forgot - APM Planner 2.0 rattles through the same procedure without a hitch. I think that points to the software rather than the hardware!

please try temporarly disabling any Bluetooth port you may have, this is just a guess, but see if it helps.

OK, thanks - that appears to have solved it.

What has puzzled me though is that the first time I tried flashing the firmware it asked if the board was AM2.5+ but I answered negative because it’s a 2.6 (was that the correct response?). Since that one time however, I’ve not seen the same question (despite uninstalling and reinstalling MP). Can anyone explain this? Firmware downloaded OK anyway.