Answering my own question here: 
Solved this by chance! I made a copy of the TM and used that instead. No more error messages or crashes. Auto-insert tags is working properly.

I am experiencing exactly the same thing (except that when I use the context menu nothing at all happens). Ctrl+Alt+Insert closes Studio. But I refuse to have to copy the TM -- surely there is something wrong with the feature if that should be necessary.

Returning here as I see Mats is also having problems with auto-insert tags.
Studio hasn't crashed since I posted the above, but I find auto-insert works only sometimes. [Edited to add: Studio has just crashed when I was testing this again!]

Right now I have a project with a TM and a single docx. file for translation. Neither the shortcut nor the context menu option works. I could put it in a package if anyone wants to have a look.

Let me know.

Emma Goldsmith

Hi Emma... if you have a support contract you should send this to the support team so they can look at it.  If you don't then can you send me the package and I'll log a case for you.

Thanks, Paul. Unfortunately, I no longer have that project in Studio. If it happens again, I'll send you the package.