Bugzilla

I somehow managed to reproduce this without crashing the browser. It occurs randomly and I couldn't figure it out what really triggers this behavior.
If it is of any help, I uploaded the profile on which it can be reproduced easily to the mozilla drive (https://drive.google.com/drive/u/1/folders/1FnrSDJc6ZpfVDgezqyTerNyhqynI528l).
It's a profile with full allowed storage reached (simulated via dom.quotaManager.temporaryStorage.fixedLimit) and with a bunch of tabs opened.

STR:
1. Launch Nightly with this profile
2. Check the Cookies and Site Data value -> it is around 12.4 GB
3. Reload all tabs
4. Check again the Cookies and Site data value -> It will be around 750 MB or so

It can be reproduced on Firefox Release as well using the same profile.  
Given that its not actually a NextGen local storage issue, but a more weird edge case as mentioned by Andrew, is the engineering team taking into account to debug/fix this as part of enabling LSNG or not?

I somehow managed to reproduce this without crashing the browser. It occurs randomly and I couldn't figure it out what really triggers this behavior. (on Windows 7)
If it is of any help, I uploaded the profile on which it can be reproduced easily to the mozilla drive (https://drive.google.com/drive/u/1/folders/1FnrSDJc6ZpfVDgezqyTerNyhqynI528l).
It's a profile with full allowed storage reached (simulated via dom.quotaManager.temporaryStorage.fixedLimit) and with a bunch of tabs opened.

STR:
1. Launch Nightly with this profile
2. Check the Cookies and Site Data value -> it is around 12.4 GB
3. Reload all tabs
4. Check again the Cookies and Site data value -> It will be around 750 MB or so

It can be reproduced on Firefox Release as well using the same profile.  
Given that its not actually a NextGen local storage issue, but a more weird edge case as mentioned by Andrew, is the engineering team taking into account to debug/fix this as part of enabling LSNG or not?