that sounds like you run in to liion issue
which cells do you use?

ecalc.ch might help to choose the rotor and look for a possible battery missmatch

You can check your own logs.
- if motor command goes to 0 while in the air, that can certainly cause instability
- if any one of your motor commands goes to 100 and stays there till you crash, plus on top your drone basically dips and and starts fast sommersaulting in that exact same corner, then very likely you are looking at desync issue (assume you have already reflashed with 24khz pwm)
- if none of the above, check your SET POINT plot versus your GYRO, it should track closely. If it diverges just as you lose control, and none of the motors are maxed out, then it could very well be your PIDs are way too loose

Edit: Missed the point that you are flying a 6S1P lion pack. What cells are you using and is the pack old? Lion packs have poor burst compared to lipos, so if you have a heavy quad carrying a heavy battery (310g? pack), power hungry motors, AND running VERY LOW THROTTLE, I think it might be normal for your drone to react slower to any fast adjustment and may add to your issue. If you have a lighter lipo pack, try it and see if you experience the same.

If you plan to do any acro flying and using low throttle, with such a setup you might want to reconsider keeping airmode on for those times.

liion is a different animal, we run many times into rapithole troubleshooting a "tune and esc" issue, but is a powerdelivery issue by liion in truth.
esc issues sounds so close to power delivery issues. that liion trend makes many good quads usless

I think I got it solved, been flying today for significant time without issues.

First I adjusted the PIDs (I have another 7" that's Betaflight but on different frame and motors, so I provided similar values). That made it behave better, but it was still flipping over when I was trying to raise up high (I think that's called roll of death?)

I then went to play with ESC settings and setting Motor Timing to MediumLow seems to have fixed it! (The default was MediumHigh). I flew for ~10 minutes, playing with throttle a lot - no issues! Of course there is probably some more tuning needed, but at least I don't have uncontrolled flipovers!

Thank you everyone for your help, highly appreciate that!

(15-Feb-2024, 01:08 PM)hugnosed_bat Wrote: liion is a different animal, we run many times into rapithole troubleshooting a "tune and esc" issue, but is a powerdelivery issue by liion in truth.
esc issues sounds so close to power delivery issues. that liion trend makes many good quads useless

This is somewhat off topic, but I chatted with iFly about whether it would be possible to negate this by placing a Lipo inline connected to a relay and triggering said relay when throttle goes above a certain setpoint, say 40%, giving an instantaneous power boost to negate the problems of Li-ion.  I was thinking in my example of using say a 300mAh or 250mAh Lipo (probably 2x 3S Lipos for 6S as they don't make 250 or 300 Lipos in 6S AFAIK).  Something that covers that "oh sh*t" situation where you need more power/amps than the Li-ion can provide for a very short window, say like a 2 sec burst.  I don't think anything like that exists within the hobby and I think you could only trigger it manually on a switch, but maybe you could add a conditional statement in mixes that would activate a channel when throttle was pushed above a certain point.  Anyway, theoretical and off topic.

(16-Feb-2024, 05:53 PM)Pathfinder075 Wrote: This is somewhat off topic, but I chatted with iFly about whether it would be possible to negate this by placing a Lipo inline connected to a relay and triggering said relay when throttle goes above a certain setpoint, say 40%, giving an instantaneous power boost to negate the problems of Li-ion.  I was thinking in my example of using say a 300mAh or 250mAh Lipo (probably 2x 3S Lipos for 6S as they don't make 250 or 300 Lipos in 6S AFAIK).  Something that covers that "oh sh*t" situation where you need more power/amps than the Li-ion can provide for a very short window, say like a 2 sec burst.  I don't think anything like that exists within the hobby and I think you could only trigger it manually on a switch, but maybe you could add a conditional statement in mixes that would activate a channel when throttle was pushed above a certain point.  Anyway, theoretical and off topic.

Interesting thought, but I don't think that would be practical. First you would basically have two packs with different IR, so think of a battery with a bad imbalanced cell, your circuit would need to prevent current flow between the packs. Second the lipo pack would need to be of significant size, 300mah is way too small, say it was able to give you 60C, that would be only 18A burst. 
You would be better off going with a high discharge li-ion, the Molicel P42A is an excellent example, 45 amp burst capable. 

The theoretical electronic design of it included a diode on the Li-ion side and the relay would prevent any current flow between the two packs when not energised. It was a theory thing. But it was more aimed at mountain surfers that need instantly more juice than a Li-ion produces, but also the possibility of spending a lot of time cruising. The hybrid LR build. I might play with one day, see what happens. What sort of pack size would you say would be enough to power out of a steep dive, i'm talking straight down dive like you might do down the side of a building. Most Li-ion would be insufficient to pull someone out of that sort of dive. Even 18A extra on top of whatever the Li-ion is dishing out might be enough. But there is nothing stopping a person using say 450 or 550mAh, it's more the weight issue with it. Anyway this is taking things way off topic. I agree on using the high discharge Li-ion, but maybe the Molicel P45B, but would be an expensive pack.

Sorry OP for taking this thread off topic...

P45B cells are slightly more expensive, around $8 each, but P42A deliver the same burst and can be found for $4-5. So if you are build your own 4S pack, it won't cost you more than $20.

Liion have no problem pulling out of dives, but that depends on your build. If it is a heavy build with heavy battery and current hungry motors then probably not. If it is a lightweight build with efficient motors, its no problem. This is a 4" toothpick with measly 2x18650 medium discharge 3400mah cells, full throttle burst pulled 21a and even after 30 minutes flying it was still putting out 18a+. It certainly doesn't react like a lipo and you will need to give throttle sooner, but for this setup it is enough amps to still do some acro.
https://youtu.be/CtcjBSfbNKI?t=19