I am setting up plasma and have run into two linked problems with crashes.

I have added and deleted a few widgets but have run into problems with one widget – it shows the language for the keyboard input – a plain box containing two letters for the language.

When I tried to delete it three things happen:
• the widget disappears – as expected
• a small empty rectangular box the same colour as my solid coloured desktop background appears in the lower right corner just above the task bar/ time display
• plasma completely freezes

The plasma freeze involves:
• cursor can’t select anything
• ctrl + alt + del takes me to the screen with re-start, power off options etc. but they do not work / respond
• holding down the power button is required for shut down

I was trying different things ->>

Trying to lock the widgets:
• successful

Trying to unlock the widgets causes:
• the machine freezes in exactly the same way as trying to delete the widget >>>
• cursor moves can’t select or do anything (neither left or right click)
• cntrl + alt + del takes you to an unresponsive power down/ restart screen
• a button down power off is required

Trying to manually remove the file:
• I’m not surely I can definitively find it in the plasmoids folder – unfortunately the folder doesn’t only hold the widgets that I have added so I risk removing a file I need
• I have searched in other files in ‘usr’ using ‘language’, ‘input’ and ‘keyboard’ strings but its not clear which file it might be
• I have google searched and gone to the kde store to see if I can find the exact widget name in English in case that helps with searching (my desktop is in French so the widget is called 'Panneau de methode de saisie') but no luck locating it

***update: I've found the file in Dolphin but there doesn't seem to be an option to delete when I right click *****

I’m new to this so I’m unsure what the options are:
• is this a bug in plasma? In the widget? Both?
• Is there some way to unlock the widgets via command line and hopefully get full control of the desktop again?
• Is there some way to identify the exact folder for the widget so I can try to delete it manually?
• Is this too complicated to fix so throwing out the install (either plasma or the whole linux install) and starting again would be easier? Especially since I’m new to plasma and linux?

I’m running Ubuntu 18.04.2 LTS, Plasma version 5.12.7, kde framework version 5.44.0.

Thanks.