There are a few problems with tracking this down. The big most important ones:
- As far as I know there are no developers that have this problem.
- We don't have a simple set of instructions to recreate the issue starting with a completely erased CC3D. I suspect that you could take two sets of "exported UAV settings", (defaults.uav and completelyinstalled.uav) and do Import UAV settings alternating one and the other several times over (with NO erases) until all the flash memory blocks were used. Then it must be erased and maybe the LP erase would fail. If someone with the problem (that can fix it using CleanFlight) could document how to break it, perhaps like this, then a developer could possibly get it to break and we could understand it.
Other important things that cloud the issue:
- The erase procedure must be followed exactly. During the erase, the board looks locked up for over 20 seconds and you MUST NOT power it off till the SystemTime counter starts counting again so it might be a user error.
- It sounds like it is a problem that started with 16.09, but there are only a finite number of flash memory blocks. Changing a setting or two only uses a small number of blocks. Installing a new version uses a lot, so it would use them up sooner, making it look like the new version is the problem. Successfully erasing settings makes the blocks all available again. I think I recall a user that went back to e.g. 15.xx still had the problem which fits with it being a problem with 15.xx all along.
- It's possible that your USB port doesn't produce enough current or your long thin cable doesn't allow enough current. It might be that adding power from your ESC/BEC after connecting USB, but before erasing, (or using a computer instead of a laptop, or a different laptop with better USB power) helps.
- It may be an issue that only happens on one OS and not another. Most users have Windows OS. I think firmware developers tend to use Linux; at least I do.
- I would bet that of the users that have this issue, all their CC3D's exhibit the issue. I recall hearing some say that they had some good ones that later turned out to be "bad". This implies either - that there is something about that user's setup that causes the issue - or that devs that can't recreate the issue just have never used all the flash blocks up (at least that may be true for me).
- If someone with a broken CC3D (won't erase with LP but will erase with CleanFlight) would be willing to send it to a dev to see if they can successfully erase it with LP, the answer would either be: yes and so the user setup has an issue (possibly not the user's fault, like doesn't work on Windows 10 Vxxxx) or no in which case the dev has a CC3D with the issue and can debug it.
- There are probably other factors that I forgot to mention while writing this.
I read the Cleanflight-method, but can't get CF to work
This sounds important. Try a different computer and different cable. CF 1.10 should work.