Wrong grouping of my entries in JabRef 3.6

Dear everyone,
My bibtex file is created when I used JabRef 2.10, and is gradually updated along with JabRef’s update. However, recently I find the grouping of my two groups is wrong, and I do not know why. Because they are not so many entries in these two groups, I am trying to re-group them manually. The very strange thing is that, when I add an entry to one group named ‘Simulation most cited’, the group will automatically add to the other subgroup named ‘Simulation’, it is a subgroup of group ‘Nanowire’.
It seems this problem appeared in recent version of JabRef. I am very confused and wondering is there any bug in group function of JabRef 3.6?
Any help would be much appreciated!

There are some problems with the grouping functionality we are already aware of (See for example https://github.com/JabRef/jabref/issues/1495 or https://github.com/JabRef/jabref/issues/1873)

However, we currently do not have the resources to fix this as this requires a major rewrite in the underlying source code. :frowning:

Thank you!
I found that, in my case, these two groups have the same first word of the group name. If I assign a new name to one of them, it seems it can fix this problem. Maybe it can be a temporary solution,
However, the sad thing is my previous assignment of many entries into these two groups has lost.:cry:

Best Regards