When Language Tool is enabled in LO, and I open a file from the LO menu - either by navigating to it, or selecting from recent files, a second menu bar is sometimes displayed. 
This behaviour does not happen if I navigate to the file in the OS file manager, caja. The behaviour does not occur if I disable the add-on.
Here are the details of my Libre Office installation:
It runs on Linux Mint:
RELEASE=19.2 CODENAME=tina EDITION="MATE" DESCRIPTION="Linux Mint 19.2 Tina" DESKTOP=Gnome TOOLKIT=GTK
First post here, so apologies if it doesn’t come out as expected - and thanks for a useful tool.