upgrade / downgrade...

did you clean the db tables before uninstalling?
In later JEM versions there is a setting for that (see image). If not, you have to do it manually.

Thank you jojo12
I am not sure to have done that before uninstall...
I'll be more carefull next time for final import.

I'am not shure, when the error occurs.
Does ist show up when you install JEM 2.1.6 or at which point you get this error message?
It sounds for me that some install/uninstall routine forgots to delete the table with the name shown in the message.

I thinks that it occurs during update.
I think too that the install/uninstall routine forgots to delete the table.
Next time, I'll do what jojo12 advised and check then database.