I took the Spark out yesterday during the awesome weather we're currently having in the UK. Went through my pre-flight, waited until I had 11 satellites, then took off. I played around for about half the battery, then switched into sports mode for a bit of a blast around. I was in a very open field at the time. I wasn't looking at the phone; I had my eyes on the Spark at all times. Suddenly I heard my phone tell me the Spark was switching to ATTI mode. I brought the Spark to a stop, but by the time I looked down at my phone it had full GPS connection again and was back in P-GPS mode. No harm done at all; I've been preparing myself for the odd blip into ATTI mode, and the Spark was close to me and in full control at all times. I'm wondering whether any of the wise forum-goers here could comment on whether bashing about in sports mode doing fast turns is more likely to force a hardware conflict and push the Spark into ATTI mode?

Actually, I've just spotted some discussion on this in another thread (https://forum.dji.com/thread-153831-1-2.html). Sounds like a similar issue.

This is the moment of my flight log that corresponds to the audio from my phone telling me the Spark was going into ATTI mode. Is this simply a case of a momentary drop in GPS signal strength and unrelated to the Spark being in sports mode? I'd appreciate any thoughts.

I fly in sports mode most of the time except capturing video but never come across a similar issue.
But my Spark has switched between ATTI & GPS at different times for no apparent reason (with more than 12 sats and high signal strength)

I will observe carefully in future.

i've stopped using sports mode no problems since

The first few times I ever flew my Spark it would momentarily jump into ATTI mode, then right back to GPS, just like you're reporting. Based on a comment I read on one of the forums, I did a careful IMU calibration. I happen to have access to a perfectly flat and level granite surface plate, so I should be able to get a calibration as good or better than the factory can. Since then I've never had the issue repeat. This weekend I went out and tossed it around in sport mode as violently as it would go, and nary a hiccup. Coincidence?  With a sample size of 1 it's impossible to tell. I wish there was some way to force ATTI mode, I would like to know if it would drift or stay still.

Yeah that was me in the post you referenced. I'm going to do another compass calibration and see if it happens again. I did notice I got a YAW error and then the compass error followed. Maybe sport mode causes too much stress on the IMU and compass to keep up? I think when it levels out, everything recovers, but still...