not all messages are getting imported from Thunderbird

I am trying out eM Client as a replacement for Thunderbird.  I successfully brought in all of my accounts and they are syncing just fine so far.  

In Thunderbird I use local folders to “archive” old emails.  I have several hundred different folders.  I did the import on these and all the folders imported just fine.  The problem is that for some of the folders, not all of the messages imported.  For example, in one folder there were 941 messages, but only 937 were imported.  In another folder there were 6673 messages, but only 6662 were imported.  I am not seeing anything unusual about the messages that did not import.

In eM Client I deleted all the messages in one of those folders and used File > Import > Import From Thunderbird > Import Selected Folders and the same thing happened.  Only 937 of the 941 messages were imported.

Is there some type of known bug or problem in importing from Thunderbird?  Some setting that I’m missing?  Any help is appreciated.


Edit:  What is even stranger is that I tried the Import Selected Folders several times and it always imports just 937 out of 941 messages for this folder, but the window that counts up the number of messages that are being imported shows xxx/923.  Despite showing that 923 messages will be imported, 937 are actually imported.